diff --git a/.gitignore b/.gitignore
index 4b84051..62b9af2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 *.pyc
+*.py.bak
 
 # Virtualenv
 venv/
@@ -7,3 +8,7 @@ venv/
 build/
 dist/
 nrfutil.egg-info/
+
+# Test artefacts
+/nordicsemi/dfu/tests/mypackage.zip
+/tests/test.zip
diff --git a/README.md b/README.md
index dce36b9..296899e 100644
--- a/README.md
+++ b/README.md
@@ -61,7 +61,7 @@ You will need to clone the present repository first to run or install nrfutil fr
 
 To install nrfutil from source the following prerequisites must be satisfied:
 
-* [Python 2.7 (2.7.10 or newer, not Python 3)](https://www.python.org/downloads/)
+* [Python 3.7](https://www.python.org/downloads/)
 * [pip](https://pip.pypa.io/en/stable/installing.html)
 * setuptools (upgrade to latest version): `pip install -U setuptools`
 
@@ -81,7 +81,7 @@ pip install -r requirements.txt
 
 You can run the program directly without installing it by executing:
 ```
-python nordicsemi/__main__.py
+python ./nordicsemi
 ```
 
 ### Installing from source
@@ -101,8 +101,6 @@ pyinstaller /full/path/to/nrfutil.spec
 
 **Note**: Some anti-virus programs will stop PyInstaller from executing correctly when it modifies the executable file.
 
-**Note**: PyInstaller on macOS may have issues with newer versions of Python 2.7.x., e.g. error message `Failed to execute script pyi_rth_pkgres` at runtime. Try rolling back to Python v2.7.10 if you experience such problems.
-
 ## Usage
 
 To get info on usage of nrfutil:
diff --git a/nordicsemi/__main__.py b/nordicsemi/__main__.py
index f826357..43a6e06 100755
--- a/nordicsemi/__main__.py
+++ b/nordicsemi/__main__.py
@@ -485,7 +485,7 @@ def display(key_file, key, format, out_file):
     if key == "pk":
         kstr = signer.get_vk(format, dbg)
     elif key == "sk":
-        kstr = "\nWARNING: Security risk! Do not share the private key.\n\n"
+        kstr = b"\nWARNING: Security risk! Do not share the private key.\n\n"
         kstr = kstr + signer.get_sk(format, dbg)
 
     if not out_file:
@@ -806,7 +806,7 @@ def generate(zipfile,
         try:
             # This will parse any string starting with 0x as base 16.
             sd_req_list = sd_req.split(',')
-            sd_req_list = map(int_as_text_to_int, sd_req_list)
+            sd_req_list = list(map(int_as_text_to_int, sd_req_list))
         except ValueError:
             raise NordicSemiException("Could not parse value for --sd-req. "
                                       "Hex values should be prefixed with 0x.")
@@ -816,7 +816,7 @@ def generate(zipfile,
         try:
             # This will parse any string starting with 0x as base 16.
             sd_id_list = sd_id.split(',')
-            sd_id_list = map(int_as_text_to_int, sd_id_list)
+            sd_id_list = list(map(int_as_text_to_int, sd_id_list))
 
             # Copy all IDs from sd_id_list to sd_req_list, without duplicates.
             # This ensures that the softdevice update can be repeated in case
@@ -867,11 +867,11 @@ def generate(zipfile,
     if zigbee:
         inner_external_app = False
 
-    if zigbee_ota_min_hw_version > 0xFFFF:
+    if zigbee_ota_min_hw_version is not None and zigbee_ota_min_hw_version > 0xFFFF:
         click.echo('Error: zigbee-ota-min-hw-version exceeds 2-byte long integer.')
         return
 
-    if zigbee_ota_max_hw_version > 0xFFFF:
+    if zigbee_ota_max_hw_version is not None and zigbee_ota_max_hw_version > 0xFFFF:
         click.echo('Error: zigbee-ota-max-hw-version exceeds 2-byte long integer.')
         return
 
@@ -1092,7 +1092,7 @@ def serial(package, port, connect_delay, flow_control, packet_receipt_notificati
 
 
 def enumerate_ports():
-    descs   = BLEDriver.enum_serial_ports()
+    descs   = list(BLEDriver.enum_serial_ports())
     if len(descs) == 0:
         return None
     click.echo('Please select connectivity serial port:')
@@ -1364,7 +1364,7 @@ def thread(package, port, address, server_port, panid, channel, jlink_snr, flash
     mcast_dfu = False
 
     if address is None:
-        address = ipaddress.ip_address(u"ff03::1")
+        address = ipaddress.ip_address("ff03::1")
         click.echo("Address not specified. Using ff03::1 (all Thread nodes)")
     else:
         try:
diff --git a/nordicsemi/bluetooth/hci/slip.py b/nordicsemi/bluetooth/hci/slip.py
index b95d97b..33a8e08 100644
--- a/nordicsemi/bluetooth/hci/slip.py
+++ b/nordicsemi/bluetooth/hci/slip.py
@@ -1,5 +1,4 @@
-#
-# Copyright (c) 2016 Nordic Semiconductor ASA
+# Copyright (c) 2016 - 2019 Nordic Semiconductor ASA
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without modification,
@@ -33,26 +32,25 @@
 # ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#
 
 import logging
 
 logger = logging.getLogger(__name__)
 
 
-class Slip(object):
-    def __init__(self):
-        self.SLIP_END = '\xc0'
-        self.SLIP_ESC = '\xdb'
-        self.SLIP_ESC_END = '\xdc'
-        self.SLIP_ESC_ESC = '\xdd'
+class Slip:
+    SLIP_END = 0xc0
+    SLIP_ESC = 0xdb
+    SLIP_ESC_END = 0xdc
+    SLIP_ESC_ESC = 0xdd
 
+    def __init__(self):
         self.started = False
         self.escaped = False
-        self.stream = ''
-        self.packet = ''
+        self.stream = bytearray()
+        self.packet = bytearray()
 
-    def append(self, data):
+    def append(self, data: bytes):
         """
         Append a new
         :param data: Append a new block of data to do decoding on when calling decode.
@@ -66,7 +64,7 @@ def decode(self):
         Decodes a package according to http://en.wikipedia.org/wiki/Serial_Line_Internet_Protocol
         :return Slip: A list of decoded slip packets
         """
-        packet_list = list()
+        packet_list = []
 
         for char in self.stream:
             if char == self.SLIP_END:
@@ -74,51 +72,51 @@ def decode(self):
                     if len(self.packet) > 0:
                         self.started = False
                         packet_list.append(self.packet)
-                        self.packet = ''
+                        self.packet = bytearray()
                 else:
                     self.started = True
-                    self.packet = ''
+                    self.packet = bytearray()
             elif char == self.SLIP_ESC:
                 self.escaped = True
             elif char == self.SLIP_ESC_END:
                 if self.escaped:
-                    self.packet += self.SLIP_END
+                    self.packet.append(self.SLIP_END)
                     self.escaped = False
                 else:
                     self.packet += char
             elif char == self.SLIP_ESC_ESC:
                 if self.escaped:
-                    self.packet += self.SLIP_ESC
+                    self.packet.append(self.SLIP_ESC)
                     self.escaped = False
                 else:
-                    self.packet += char
+                    self.packet.append(char)
             else:
                 if self.escaped:
                     logging.error("Error in SLIP packet, ignoring error.")
-                    self.packet = ''
+                    self.packet = bytearray()
                     self.escaped = False
                 else:
-                    self.packet += char
+                    self.packet.append(char)
 
-        self.stream = ''
+        self.stream.clear()
 
         return packet_list
 
-    def encode(self, packet):
+    def encode(self, packet: bytes):
         """
         Encode a packet according to SLIP.
         :param packet: A str array that represents the package
         :return: str array with an encoded SLIP packet
         """
-        encoded = self.SLIP_END
+        encoded = bytearray([self.SLIP_END])
 
         for char in packet:
             if char == self.SLIP_END:
-                encoded += self.SLIP_ESC + self.SLIP_ESC_END
+                encoded.extend([self.SLIP_ESC, self.SLIP_ESC_END])
             elif char == self.SLIP_ESC:
-                encoded += self.SLIP_ESC + self.SLIP_ESC_ESC
+                encoded.extend([self.SLIP_ESC, self.SLIP_ESC_ESC])
             else:
-                encoded += char
-        encoded += self.SLIP_END
+                encoded.append(char)
+        encoded.append(self.SLIP_END)
 
         return encoded
diff --git a/nordicsemi/bluetooth/hci/tests/test_codec.py b/nordicsemi/bluetooth/hci/tests/test_codec.py
index b0d2a62..8967d2e 100644
--- a/nordicsemi/bluetooth/hci/tests/test_codec.py
+++ b/nordicsemi/bluetooth/hci/tests/test_codec.py
@@ -64,7 +64,7 @@ def test_decode_packet(self):
 
         for uart_packet in read_packets:
             hex_string = uart_packet.replace(" ", "")
-            hex_data = hex_string.decode("hex")
+            hex_data = bytes.fromhex(hex_string)
             slip.append(hex_data)
 
         packets = slip.decode()
diff --git a/nordicsemi/dfu/bl_dfu_sett.py b/nordicsemi/dfu/bl_dfu_sett.py
index f0b71cf..32111b7 100755
--- a/nordicsemi/dfu/bl_dfu_sett.py
+++ b/nordicsemi/dfu/bl_dfu_sett.py
@@ -47,7 +47,6 @@
 
 # 3rd party libraries
 import intelhex
-from intelhex import IntelHexError
 
 # Nordic libraries
 from nordicsemi.dfu.nrfhex import *
@@ -112,8 +111,7 @@ class BLDFUSettings(object):
     bl_sett_52840_addr    = 0x000FF000
     bl_sett_backup_offset = 0x1000
 
-
-    def __init__(self, ):
+    def __init__(self):
         """
         """
         # instantiate a hex object
@@ -168,7 +166,7 @@ def _calculate_crc32_from_hex(self, ih_object, start_addr=None, end_addr=None):
         list = []
         if start_addr == None and end_addr == None:
             hex_dict = ih_object.todict()
-            for addr, byte in hex_dict.items():
+            for addr, byte in list(hex_dict.items()):
                 list.append(byte)
         else:
             for addr in range(start_addr, end_addr + 1):
@@ -215,21 +213,22 @@ def generate(self, arch, app_file, app_ver, bl_ver, bl_sett_ver, custom_bl_sett_
                 self.app_boot_validation_bytes = struct.pack('<I', self.app_crc)
             elif app_boot_validation_type == 'VALIDATE_GENERATED_SHA256':
                 self.app_boot_validation_type = 2 & 0xffffffff
-                sha256 = Package.calculate_sha256_hash(self.app_bin)
-                self.app_boot_validation_bytes = bytearray([int(binascii.hexlify(i), 16) for i in list(sha256)][31::-1])
+                # Package.calculate_sha256_hash gives a reversed
+                # digest. It need to be reversed back to a normal
+                # sha256 digest.
+                self.app_boot_validation_bytes = Package.calculate_sha256_hash(self.app_bin)[::-1]
             elif app_boot_validation_type == 'VALIDATE_ECDSA_P256_SHA256':
                 self.app_boot_validation_type = 3 & 0xffffffff
-                ecdsa = Package.sign_firmware(key_file, self.app_bin)
-                self.app_boot_validation_bytes = bytearray([int(binascii.hexlify(i), 16) for i in list(ecdsa)])
+                self.app_boot_validation_bytes = Package.sign_firmware(key_file, self.app_bin)
             else:  # This also covers 'NO_VALIDATION' case
                 self.app_boot_validation_type = 0 & 0xffffffff
-                self.app_boot_validation_bytes = bytearray(0)
+                self.app_boot_validation_bytes = bytes(0)
         else:
             self.app_sz = 0x0 & 0xffffffff
             self.app_crc = 0x0 & 0xffffffff
             self.bank0_bank_code = 0x0 & 0xffffffff
             self.app_boot_validation_type = 0x0 & 0xffffffff
-            self.app_boot_validation_bytes = bytearray(0)
+            self.app_boot_validation_bytes = bytes(0)
 
         if sd_file is not None:
             # Load SD to calculate CRC
@@ -254,19 +253,20 @@ def generate(self, arch, app_file, app_ver, bl_ver, bl_sett_ver, custom_bl_sett_
                 self.sd_boot_validation_bytes = struct.pack('<I', sd_crc)
             elif sd_boot_validation_type == 'VALIDATE_GENERATED_SHA256':
                 self.sd_boot_validation_type = 2 & 0xffffffff
-                sha256 = Package.calculate_sha256_hash(self.sd_bin)
-                self.sd_boot_validation_bytes = bytearray([int(binascii.hexlify(i), 16) for i in list(sha256)][31::-1])
+                # Package.calculate_sha256_hash gives a reversed
+                # digest. It need to be reversed back to a normal
+                # sha256 digest.
+                self.sd_boot_validation_bytes = Package.calculate_sha256_hash(self.sd_bin)[::-1]
             elif sd_boot_validation_type == 'VALIDATE_ECDSA_P256_SHA256':
                 self.sd_boot_validation_type = 3 & 0xffffffff
-                ecdsa = Package.sign_firmware(key_file, self.sd_bin)
-                self.sd_boot_validation_bytes = bytearray([int(binascii.hexlify(i), 16) for i in list(ecdsa)])
+                self.sd_boot_validation_bytes = Package.sign_firmware(key_file, self.sd_bin)
             else:  # This also covers 'NO_VALIDATION_CASE'
                 self.sd_boot_validation_type = 0 & 0xffffffff
-                self.sd_boot_validation_bytes = bytearray(0)
+                self.sd_boot_validation_bytes = bytes(0)
         else:
             self.sd_sz = 0x0 & 0xffffffff
             self.sd_boot_validation_type = 0 & 0xffffffff
-            self.sd_boot_validation_bytes = bytearray(0)
+            self.sd_boot_validation_bytes = bytes(0)
 
         # additional harcoded values
         self.bank_layout = 0x0 & 0xffffffff
diff --git a/nordicsemi/dfu/crc16.py b/nordicsemi/dfu/crc16.py
index aa7bc80..11de1a7 100644
--- a/nordicsemi/dfu/crc16.py
+++ b/nordicsemi/dfu/crc16.py
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2016 Nordic Semiconductor ASA
+# Copyright (c) 2019 Nordic Semiconductor ASA
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without modification,
@@ -35,7 +35,7 @@
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 
-def calc_crc16(binary_data, crc=0xffff):
+def calc_crc16(binary_data: bytes, crc=0xffff):
     """
     Calculates CRC16 on binary_data
 
@@ -46,7 +46,6 @@ def calc_crc16(binary_data, crc=0xffff):
 
     for b in binary_data:
         crc = (crc >> 8 & 0x00FF) | (crc << 8 & 0xFF00)
-        crc ^= ord(b)
         crc ^= (crc & 0x00FF) >> 4
         crc ^= (crc << 8) << 4
         crc ^= ((crc & 0x00FF) << 4) << 1
diff --git a/nordicsemi/dfu/dfu_transport.py b/nordicsemi/dfu/dfu_transport.py
index 939dd88..1910f78 100644
--- a/nordicsemi/dfu/dfu_transport.py
+++ b/nordicsemi/dfu/dfu_transport.py
@@ -1,5 +1,4 @@
-#
-# Copyright (c) 2016 Nordic Semiconductor ASA
+# Copyright (c) 2016 - 2019 Nordic Semiconductor ASA
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without modification,
@@ -33,12 +32,11 @@
 # ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#
 
-# Python specific imports
-import abc
 import logging
 
+from abc import ABC, abstractmethod
+
 # Nordic Semiconductor imports
 
 logger = logging.getLogger(__name__)
@@ -54,7 +52,7 @@ class DfuEvent:
     PROGRESS_EVENT = 1
 
 
-class DfuTransport(object):
+class DfuTransport(ABC):
     """
     This class as an abstract base class inherited from when implementing transports.
 
@@ -62,7 +60,6 @@ class DfuTransport(object):
     than this class describes. But the intent is that the implementer shall follow the semantic as
     best as she can.
     """
-    __metaclass__ = abc.ABCMeta
 
     OP_CODE = {
         'CreateObject'          : 0x01,
@@ -105,12 +102,12 @@ class DfuTransport(object):
         "The requested firmware to update was already present on the system.",
     ]
 
-    @abc.abstractmethod
+    @abstractmethod
     def __init__(self):
         self.callbacks = {}
 
 
-    @abc.abstractmethod
+    @abstractmethod
     def open(self):
         """
         Open a port if appropriate for the transport.
@@ -119,7 +116,7 @@ def open(self):
         pass
 
 
-    @abc.abstractmethod
+    @abstractmethod
     def close(self):
         """
         Close a port if appropriate for the transport.
@@ -127,7 +124,7 @@ def close(self):
         """
         pass
 
-    @abc.abstractmethod
+    @abstractmethod
     def send_init_packet(self, init_packet):
         """
         Send init_packet to device.
@@ -140,7 +137,7 @@ def send_init_packet(self, init_packet):
         pass
 
 
-    @abc.abstractmethod
+    @abstractmethod
     def send_firmware(self, firmware):
         """
         Start sending firmware to device.
@@ -176,6 +173,6 @@ def _send_event(self, event_type, **kwargs):
         :param kwargs: Arguments to callback function
         :return:
         """
-        if event_type in self.callbacks.keys():
+        if event_type in list(self.callbacks.keys()):
             for callback in self.callbacks[event_type]:
                 callback(**kwargs)
diff --git a/nordicsemi/dfu/dfu_transport_ant.py b/nordicsemi/dfu/dfu_transport_ant.py
index ceead23..03f4655 100755
--- a/nordicsemi/dfu/dfu_transport_ant.py
+++ b/nordicsemi/dfu/dfu_transport_ant.py
@@ -39,7 +39,7 @@
 import binascii
 from datetime import datetime, timedelta
 import logging
-import Queue
+import queue
 import struct
 import sys
 
@@ -132,7 +132,7 @@ def __init__(self, ant_dev, timeout, search_timeout, ant_config):
         self.tx_seq = None
         self.rx_seq = None
         self.rx_data = None
-        self.resp_queue = Queue.Queue()
+        self.resp_queue = queue.Queue()
 
     def open(self):
         # TODO: use constant from antlib when it exists.
@@ -187,7 +187,7 @@ def send_message(self, req):
         logger.log(TRANSPORT_LOGGING_LEVEL, "ANT: --> {}".format(req))
 
         self.tx_seq = (self.tx_seq + 1) & 0xFF
-        data = map(ord, struct.pack('<HB', len(req) + 3, self.tx_seq)) + req
+        data = list(struct.pack('<HB', len(req) + 3, self.tx_seq)) + req
 
         self.tx_result = None
 
@@ -461,7 +461,7 @@ def try_to_recover():
     def __set_prn(self):
         logger.debug("ANT: Set Packet Receipt Notification {}".format(self.prn))
         self.dfu_adapter.send_message([DfuTransportAnt.OP_CODE['SetPRN']]
-            + map(ord, struct.pack('<H', self.prn)))
+            + list(struct.pack('<H', self.prn)))
         self.__get_response(DfuTransportAnt.OP_CODE['SetPRN'])
 
     def __get_mtu(self):
@@ -506,7 +506,7 @@ def __create_data(self, size):
 
     def __create_object(self, object_type, size):
         self.dfu_adapter.send_message([DfuTransportAnt.OP_CODE['CreateObject'], object_type]\
-                                            + map(ord, struct.pack('<L', size)))
+                                            + list(struct.pack('<L', size)))
         self.__get_response(DfuTransportAnt.OP_CODE['CreateObject'])
 
     def __calculate_checksum(self):
@@ -563,7 +563,7 @@ def validate_crc():
             to_transmit = data[i:i + self.mtu - 4 ]
             to_transmit = struct.pack('B',DfuTransportAnt.OP_CODE['WriteObject']) + to_transmit
 
-            self.dfu_adapter.send_message(map(ord, to_transmit))
+            self.dfu_adapter.send_message(list(to_transmit))
             crc     = binascii.crc32(to_transmit[1:], crc) & 0xFFFFFFFF
             offset += len(to_transmit) - 1
             current_pnr    += 1
@@ -577,7 +577,7 @@ def validate_crc():
 
     def __get_response(self, operation):
         def get_dict_key(dictionary, value):
-            return next((key for key, val in dictionary.items() if val == value), None)
+            return next((key for key, val in list(dictionary.items()) if val == value), None)
 
         resp = self.dfu_adapter.get_message()
 
diff --git a/nordicsemi/dfu/dfu_transport_ble.py b/nordicsemi/dfu/dfu_transport_ble.py
index e7926ce..6bf71aa 100644
--- a/nordicsemi/dfu/dfu_transport_ble.py
+++ b/nordicsemi/dfu/dfu_transport_ble.py
@@ -40,17 +40,16 @@
 import sys
 import time
 import wrapt
-import Queue
+import queue
 import struct
 import logging
 import binascii
 
-from types                          import NoneType
 from nordicsemi.dfu.dfu_transport   import DfuTransport, DfuEvent
 from pc_ble_driver_py.exceptions    import NordicSemiException, IllegalStateException
 from pc_ble_driver_py.ble_driver    import BLEDriver, BLEDriverObserver, BLEEnableParams, BLEUUIDBase, BLEGapSecKDist, BLEGapSecParams, \
     BLEGapIOCaps, BLEUUID, BLEAdvData, BLEGapConnParams, BLEEvtID, BLEGattHVXType, NordicSemiErrorCheck, BLEGapSecStatus, driver
-from pc_ble_driver_py.ble_driver    import ATT_MTU_DEFAULT
+from pc_ble_driver_py.ble_driver    import ATT_MTU_DEFAULT, BLEConfig, BLEConfigConnGatt
 from pc_ble_driver_py.ble_adapter   import BLEAdapter, BLEAdapterObserver, EvtSync
 
 logger  = logging.getLogger(__name__)
@@ -95,8 +94,8 @@ def __init__(self, adapter, bonded=False, keyset=None):
         self.adapter            = adapter
         self.bonded             = bonded
         self.keyset             = keyset
-        self.notifications_q    = Queue.Queue()
-        self.indication_q       = Queue.Queue()
+        self.notifications_q    = queue.Queue()
+        self.indication_q       = queue.Queue()
         self.att_mtu            = ATT_MTU_DEFAULT
         self.packet_size        = self.att_mtu - 3
         self.adapter.observer_register(self)
@@ -104,16 +103,27 @@ def __init__(self, adapter, bonded=False, keyset=None):
 
     def open(self):
         self.adapter.driver.open()
-        ble_enable_params = BLEEnableParams(vs_uuid_count      = 10,
-                                            service_changed    = True,
-                                            periph_conn_count  = 0,
-                                            central_conn_count = 1,
-                                            central_sec_count  = 1)
-        if nrf_sd_ble_api_ver >= 3:
-            logger.info("\nBLE: ble_enable with local ATT MTU: {}".format(DFUAdapter.LOCAL_ATT_MTU))
-            ble_enable_params.att_mtu = DFUAdapter.LOCAL_ATT_MTU
 
-        self.adapter.driver.ble_enable(ble_enable_params)
+        assert nrf_sd_ble_api_ver in [2, 5]
+
+        if nrf_sd_ble_api_ver == 2:
+            self.adapter.driver.ble_enable(
+                BLEEnableParams(
+                    vs_uuid_count = 10,
+                    service_changed = True,
+                    periph_conn_count = 0,
+                    central_conn_count = 1,
+                    central_sec_count = 1,
+                )
+            )
+
+        if nrf_sd_ble_api_ver == 5:
+            self.adapter.driver.ble_cfg_set(
+                BLEConfig.conn_gatt,
+                BLEConfigConnGatt(att_mtu=DFUAdapter.LOCAL_ATT_MTU),
+            )
+            self.adapter.driver.ble_enable()
+
         self.adapter.driver.ble_vs_uuid_add(DFUAdapter.BASE_UUID)
 
     def close(self):
@@ -159,7 +169,7 @@ def connect(self, target_device_name, target_device_addr):
         if nrf_sd_ble_api_ver >= 3:
             if DFUAdapter.LOCAL_ATT_MTU > ATT_MTU_DEFAULT:
                 logger.info('BLE: Enabling longer ATT MTUs')
-                self.att_mtu = self.adapter.att_mtu_exchange(self.conn_handle)
+                self.att_mtu = self.adapter.att_mtu_exchange(self.conn_handle, DFUAdapter.LOCAL_ATT_MTU)
             else:
                 logger.info('BLE: Using default ATT MTU')
 
@@ -371,7 +381,12 @@ def on_gap_evt_adv_report(self, ble_driver, conn_handle, peer_addr, rssi, adv_ty
                                                 slave_latency        = 0)
             logger.info('BLE: Found target advertiser, address: 0x{}, name: {}'.format(address_string, dev_name))
             logger.info('BLE: Connecting to 0x{}'.format(address_string))
-            self.adapter.connect(address = peer_addr, conn_params = self.conn_params)
+            # Connect must specify tag=1 to enable the settings
+            # set with BLEConfigConnGatt (that implictly operates
+            # on connections with tag 1) to allow for larger MTU.
+            self.adapter.connect(address=peer_addr,
+                                 conn_params=self.conn_params,
+                                 tag=1)
             # store the address for subsequent connections
             self.target_device_addr = address_string
             self.target_device_addr_type = peer_addr
@@ -426,7 +441,7 @@ def __init__(self,
                  att_mtu,
                  target_device_name=None,
                  target_device_addr=None,
-                 baud_rate=115200,
+                 baud_rate=1000000,
                  prn=0):
         super(DfuTransportBle, self).__init__()
         DFUAdapter.LOCAL_ATT_MTU = att_mtu
@@ -560,7 +575,7 @@ def try_to_recover():
 
     def __set_prn(self):
         logger.debug("BLE: Set Packet Receipt Notification {}".format(self.prn))
-        self.dfu_adapter.write_control_point([DfuTransportBle.OP_CODE['SetPRN']] + map(ord, struct.pack('<H', self.prn)))
+        self.dfu_adapter.write_control_point([DfuTransportBle.OP_CODE['SetPRN']] + list(struct.pack('<H', self.prn)))
         self.__get_response(DfuTransportBle.OP_CODE['SetPRN'])
 
     def __create_command(self, size):
@@ -571,7 +586,7 @@ def __create_data(self, size):
 
     def __create_object(self, object_type, size):
         self.dfu_adapter.write_control_point([DfuTransportBle.OP_CODE['CreateObject'], object_type]\
-                                            + map(ord, struct.pack('<L', size)))
+                                            + list(struct.pack('<L', size)))
         self.__get_response(DfuTransportBle.OP_CODE['CreateObject'])
 
     def __calculate_checksum(self):
@@ -619,7 +634,7 @@ def validate_crc():
         current_pnr = 0
         for i in range(0, len(data), self.dfu_adapter.packet_size):
             to_transmit     = data[i:i + self.dfu_adapter.packet_size]
-            self.dfu_adapter.write_data_point(map(ord, to_transmit))
+            self.dfu_adapter.write_data_point(list(to_transmit))
             crc     = binascii.crc32(to_transmit, crc) & 0xFFFFFFFF
             offset += len(to_transmit)
             current_pnr    += 1
@@ -635,11 +650,11 @@ def validate_crc():
 
     def __get_response(self, operation):
         def get_dict_key(dictionary, value):
-            return next((key for key, val in dictionary.items() if val == value), None)
+            return next((key for key, val in list(dictionary.items()) if val == value), None)
 
         try:
             resp = self.dfu_adapter.notifications_q.get(timeout=DfuTransportBle.DEFAULT_TIMEOUT)
-        except Queue.Empty:
+        except queue.Empty:
             raise NordicSemiException('Timeout: operation - {}'.format(get_dict_key(DfuTransportBle.OP_CODE,
                                                                                     operation)))
 
diff --git a/nordicsemi/dfu/dfu_transport_serial.py b/nordicsemi/dfu/dfu_transport_serial.py
index d2e9477..20bd787 100644
--- a/nordicsemi/dfu/dfu_transport_serial.py
+++ b/nordicsemi/dfu/dfu_transport_serial.py
@@ -356,7 +356,7 @@ def __is_device_in_bootloader_mode(self, device):
     def __set_prn(self):
         logger.debug("Serial: Set Packet Receipt Notification {}".format(self.prn))
         self.dfu_adapter.send_message([DfuTransportSerial.OP_CODE['SetPRN']]
-            + map(ord, struct.pack('<H', self.prn)))
+            + list(struct.pack('<H', self.prn)))
         self.__get_response(DfuTransportSerial.OP_CODE['SetPRN'])
 
     def __get_mtu(self):
@@ -401,7 +401,7 @@ def __create_data(self, size):
 
     def __create_object(self, object_type, size):
         self.dfu_adapter.send_message([DfuTransportSerial.OP_CODE['CreateObject'], object_type]\
-                                            + map(ord, struct.pack('<L', size)))
+                                            + list(struct.pack('<L', size)))
         self.__get_response(DfuTransportSerial.OP_CODE['CreateObject'])
 
     def __calculate_checksum(self):
@@ -456,14 +456,14 @@ def validate_crc():
 
         current_pnr     = 0
 
-        for i in range(0, len(data), (self.mtu-1)/2 - 1):
+        for i in range(0, len(data), (self.mtu-1)//2 - 1):
             # append the write data opcode to the front
             # here the maximum data size is self.mtu/2,
             # due to the slip encoding which at maximum doubles the size
-            to_transmit = data[i:i + (self.mtu-1)/2 - 1 ]
+            to_transmit = data[i:i + (self.mtu-1)//2 - 1 ]
             to_transmit = struct.pack('B',DfuTransportSerial.OP_CODE['WriteObject']) + to_transmit
 
-            self.dfu_adapter.send_message(map(ord, to_transmit))
+            self.dfu_adapter.send_message(list(to_transmit))
             crc     = binascii.crc32(to_transmit[1:], crc) & 0xFFFFFFFF
             offset += len(to_transmit) - 1
             current_pnr    += 1
@@ -477,7 +477,7 @@ def validate_crc():
 
     def __get_response(self, operation):
         def get_dict_key(dictionary, value):
-            return next((key for key, val in dictionary.items() if val == value), None)
+            return next((key for key, val in list(dictionary.items()) if val == value), None)
 
         resp = self.dfu_adapter.get_message()
 
diff --git a/nordicsemi/dfu/init_packet_pb.py b/nordicsemi/dfu/init_packet_pb.py
index 0653a96..bcf8bbf 100644
--- a/nordicsemi/dfu/init_packet_pb.py
+++ b/nordicsemi/dfu/init_packet_pb.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 #
 # Copyright (c) 2016 Nordic Semiconductor ASA
 # All rights reserved.
diff --git a/nordicsemi/dfu/manifest.py b/nordicsemi/dfu/manifest.py
index e2480c7..2d3d7e5 100644
--- a/nordicsemi/dfu/manifest.py
+++ b/nordicsemi/dfu/manifest.py
@@ -92,7 +92,7 @@ def remove_none_entries(d):
             if not isinstance(d, dict):
                 return d
 
-            return dict((k, remove_none_entries(v)) for k, v in d.iteritems() if v is not None)
+            return dict((k, remove_none_entries(v)) for k, v in d.items() if v is not None)
 
         return json.dumps({'manifest': self.manifest},
                           default=lambda o: remove_none_entries(o.__dict__),
diff --git a/nordicsemi/dfu/nrfhex.py b/nordicsemi/dfu/nrfhex.py
index cd9f5e3..8bf8e45 100644
--- a/nordicsemi/dfu/nrfhex.py
+++ b/nordicsemi/dfu/nrfhex.py
@@ -116,7 +116,7 @@ def get_softdevice_variant(self):
         if self.address_has_magic_number(potential_magic_number_address):
             return "s1x0"
 
-        for i in xrange(4):
+        for i in range(4):
             potential_magic_number_address += nRFHex.info_struct_address_offset
 
             if self.address_has_magic_number(potential_magic_number_address):
@@ -153,7 +153,7 @@ def size(self):
 
         # Round up to nearest word
         word_size = 4
-        number_of_words = (size + (word_size - 1)) / word_size
+        number_of_words = (size + (word_size - 1)) // word_size
         size = number_of_words * word_size
 
         return size
diff --git a/nordicsemi/dfu/package.py b/nordicsemi/dfu/package.py
index 5a84f4b..b6627fe 100644
--- a/nordicsemi/dfu/package.py
+++ b/nordicsemi/dfu/package.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 #
 # Copyright (c) 2016 Nordic Semiconductor ASA
 # All rights reserved.
@@ -241,11 +241,11 @@ def parse_package(self, filename, preserve_work_dir=False):
         self.zip_file = filename
         self.zip_dir  = os.path.join(self.work_dir, 'unpacked_zip')
         self.manifest = Package.unpack_package(filename, self.zip_dir)
-        
+
         self.rm_work_dir(preserve_work_dir)
 
     def image_str(self, index, hex_type, img):
-        type_strs = {HexType.SD_BL : "sd_bl", 
+        type_strs = {HexType.SD_BL : "sd_bl",
                     HexType.SOFTDEVICE : "softdevice",
                     HexType.BOOTLOADER : "bootloader",
                     HexType.APPLICATION : "application",
@@ -329,7 +329,7 @@ def image_str(self, index, hex_type, img):
         return s
 
     def __str__(self):
-        
+
         imgs = ""
         i = 0
         if self.manifest.softdevice_bootloader:
@@ -406,7 +406,7 @@ def generate_package(self, filename, preserve_work_dir=False):
             sd_bin_path = os.path.join(self.work_dir, sd_bin)
             sd_bin_created = True
 
-        for key, firmware_data in self.firmwares_data.iteritems():
+        for key, firmware_data in self.firmwares_data.items():
 
             # Normalize the firmware file and store it in the work directory
             firmware_data[FirmwareKeys.BIN_FILENAME] = \
@@ -439,7 +439,7 @@ def generate_package(self, filename, preserve_work_dir=False):
                     else:
                         boot_validation_bytes_array.append(Package.sign_firmware(self.key_file, bin_file_path))
                 else:
-                    boot_validation_bytes_array.append('')
+                    boot_validation_bytes_array.append(b'')
 
 
             init_packet = InitPacketPB(
@@ -599,7 +599,7 @@ def __add_firmware_info(self, firmware_type, firmware_version, filename, init_pa
         if firmware_type == HexType.SD_BL:
             self.firmwares_data[firmware_type][FirmwareKeys.SD_SIZE] = sd_size
             self.firmwares_data[firmware_type][FirmwareKeys.BL_SIZE] = bl_size
-        
+
         if firmware_version is not None:
             self.firmwares_data[firmware_type][FirmwareKeys.INIT_PACKET_DATA][PacketField.FW_VERSION] = firmware_version
 
diff --git a/nordicsemi/dfu/signing.py b/nordicsemi/dfu/signing.py
index 700fcb7..e9c67ac 100644
--- a/nordicsemi/dfu/signing.py
+++ b/nordicsemi/dfu/signing.py
@@ -1,4 +1,4 @@
-from __future__ import print_function
+
 #
 # Copyright (c) 2016 Nordic Semiconductor ASA
 # All rights reserved.
@@ -75,7 +75,7 @@ def gen_key(self, filename):
         """
         self.sk = SigningKey.generate(curve=NIST256p)
 
-        with open(filename, "w") as sk_file:
+        with open(filename, "wb") as sk_file:
             sk_file.write(self.sk.to_pem())
 
     def load_key(self, filename):
@@ -88,8 +88,6 @@ def load_key(self, filename):
             sk_pem = sk_file.read()
 
         self.sk = SigningKey.from_pem(sk_pem)
-
-        sk_hex = "".join(c.encode('hex') for c in self.sk.to_string())
         return default_sk.to_string() == self.sk.to_string()
 
     def sign(self, init_packet_data):
@@ -166,17 +164,13 @@ def get_sk_hex(self):
         if self.sk is None:
             raise IllegalStateException("Can't get key. No key created/loaded")
 
-        sk_hexlify = binascii.hexlify(self.sk.to_string())
-
-        sk_hexlify_list = []
-        for i in xrange(len(sk_hexlify)-2, -2, -2):
-            sk_hexlify_list.append(sk_hexlify[i:i+2])
-
-        sk_hexlify_list_str = ''.join(sk_hexlify_list)
+        # Reverse the key for display. This emulates a memory
+        # dump of the key interpreted a 256bit litte endian
+        # integer.
+        key = self.sk.to_string()
+        displayed_key = key[::-1].hex()
 
-        vk_hex = "Private (signing) key sk:\n{0}".format(sk_hexlify_list_str)
-
-        return vk_hex
+        return f"Private (signing) key sk:\n{displayed_key}"
 
     def get_vk_hex(self):
         """
@@ -185,21 +179,13 @@ def get_vk_hex(self):
         if self.sk is None:
             raise IllegalStateException("Can't get key. No key created/loaded")
 
-        vk = self.sk.get_verifying_key()
-        vk_hexlify = binascii.hexlify(vk.to_string())
-
-        vk_hexlify_list = []
-        for i in xrange(len(vk_hexlify[0:64])-2, -2, -2):
-            vk_hexlify_list.append(vk_hexlify[i:i+2])
+        # Reverse the two halves of key for display. This
+        # emulates a memory dump of the key interpreted as two
+        # 256bit litte endian integers.
+        key = self.sk.get_verifying_key().to_string()
+        displayed_key = (key[:32][::-1] + key[32:][::-1]).hex()
 
-        for i in xrange(len(vk_hexlify)-2, 62, -2):
-            vk_hexlify_list.append(vk_hexlify[i:i+2])
-
-        vk_hexlify_list_str = ''.join(vk_hexlify_list)
-
-        vk_hex = "Public (verification) key pk:\n{0}".format(vk_hexlify_list_str)
-
-        return vk_hex
+        return f"Public (verification) key pk:\n{displayed_key}"
 
     def wrap_code(self, key_code, dbg):
 
@@ -214,7 +200,7 @@ def wrap_code(self, key_code, dbg):
 /* This file was generated with a throwaway private key, that is only inteded for a debug version of the DFU project.
   Please see https://github.com/NordicSemiconductor/pc-nrfutil/blob/master/README.md to generate a valid public key. */
 
-#ifdef NRF_DFU_DEBUG_VERSION 
+#ifdef NRF_DFU_DEBUG_VERSION
 """
         dbg_footer="""
 #else
@@ -235,20 +221,12 @@ def get_vk_code(self, dbg):
         if self.sk is None:
             raise IllegalStateException("Can't get key. No key created/loaded")
 
-        vk = self.sk.get_verifying_key()
-        vk_hex = binascii.hexlify(vk.to_string())
-
-        vk_x_separated = ""
-        vk_x_str = vk_hex[0:64]
-        for i in xrange(0, len(vk_x_str), 2):
-            vk_x_separated = "0x" + vk_x_str[i:i+2] + ", " + vk_x_separated
-
-        vk_y_separated = ""
-        vk_y_str = vk_hex[64:128]
-        for i in xrange(0, len(vk_y_str), 2):
-            vk_y_separated = "0x" + vk_y_str[i:i+2] + ", " + vk_y_separated
-        vk_y_separated = vk_y_separated[:-2]
-        
+        to_two_digit_hex_with_0x = '0x{0:02x}'.format
+
+        key = self.sk.get_verifying_key().to_string()
+        vk_x_separated = ', '.join(map(to_two_digit_hex_with_0x, key[:64]))
+        vk_y_separated = ', '.join(map(to_two_digit_hex_with_0x, key[64:]))
+
         key_code ="""
 /** @brief Public key used to verify DFU images */
 __ALIGN(4) const uint8_t pk[64] =
diff --git a/nordicsemi/dfu/tests/firmwares/.gitignore b/nordicsemi/dfu/tests/firmwares/.gitignore
new file mode 100644
index 0000000..e9a333a
--- /dev/null
+++ b/nordicsemi/dfu/tests/firmwares/.gitignore
@@ -0,0 +1,4 @@
+# Artefacts generated during test run
+/bar.bin
+/foobar.bin
+/foo.bin
diff --git a/nordicsemi/dfu/tests/test_bl_dfu_sett.py b/nordicsemi/dfu/tests/test_bl_dfu_sett.py
index 3c76c8d..182e9ff 100644
--- a/nordicsemi/dfu/tests/test_bl_dfu_sett.py
+++ b/nordicsemi/dfu/tests/test_bl_dfu_sett.py
@@ -169,7 +169,7 @@ def test_generate_with_backup_page_check_size(self):
                           sd_file=None,
                           key_file=None)
 
-        self.assertEqual(len(settings.ihex.todict().keys()), len(settings_raw.ihex.todict().keys()) * 2)
+        self.assertEqual(len(list(settings.ihex.todict().keys())), len(list(settings_raw.ihex.todict().keys())) * 2)
 
     def test_generate_with_backup_page_check_values(self):
         settings = BLDFUSettings()
@@ -186,8 +186,8 @@ def test_generate_with_backup_page_check_values(self):
                           sd_file=None,
                           key_file=None)
 
-        backup_dict = {(k + settings.bl_sett_backup_offset): v for k, v in settings.ihex.todict().items() if k < settings.bl_sett_addr}
-        settings_dict = {k: v for k, v in settings.ihex.todict().items() if k >= settings.bl_sett_addr}
+        backup_dict = {(k + settings.bl_sett_backup_offset): v for k, v in list(settings.ihex.todict().items()) if k < settings.bl_sett_addr}
+        settings_dict = {k: v for k, v in list(settings.ihex.todict().items()) if k >= settings.bl_sett_addr}
         self.assertEqual(backup_dict, settings_dict)
 
     def test_generate_with_backup_page_custom_address(self):
@@ -206,7 +206,7 @@ def test_generate_with_backup_page_custom_address(self):
                           key_file=None)
 
         self.assertEqual(settings.backup_address, 0x0006F000)
-        self.assertTrue(0x0006F000 in settings.ihex.todict().keys())
+        self.assertTrue(0x0006F000 in list(settings.ihex.todict().keys()))
 
     def test_generate_with_backup_page_default_address(self):
         settings = BLDFUSettings()
@@ -224,7 +224,7 @@ def test_generate_with_backup_page_default_address(self):
                           key_file=None)
 
         self.assertEqual(settings.backup_address, (0x0006F000 - settings.bl_sett_backup_offset))
-        self.assertTrue((0x0006F000 - settings.bl_sett_backup_offset) in settings.ihex.todict().keys())
+        self.assertTrue((0x0006F000 - settings.bl_sett_backup_offset) in list(settings.ihex.todict().keys()))
 
 class TestBLDFUSettingsV2(unittest.TestCase):
     def setUp(self):
@@ -369,7 +369,7 @@ def test_generate_with_backup_page_check_size(self):
                           sd_file=None,
                           key_file=None)
 
-        self.assertEqual(len(settings.ihex.todict().keys()), len(settings_raw.ihex.todict().keys()) * 2)
+        self.assertEqual(len(list(settings.ihex.todict().keys())), len(list(settings_raw.ihex.todict().keys())) * 2)
 
     def test_generate_with_backup_page_check_values(self):
         settings = BLDFUSettings()
@@ -386,8 +386,8 @@ def test_generate_with_backup_page_check_values(self):
                           sd_file=None,
                           key_file=None)
 
-        backup_dict = {(k + settings.bl_sett_backup_offset): v for k, v in settings.ihex.todict().items() if k < settings.bl_sett_addr}
-        settings_dict = {k: v for k, v in settings.ihex.todict().items() if k >= settings.bl_sett_addr}
+        backup_dict = {(k + settings.bl_sett_backup_offset): v for k, v in list(settings.ihex.todict().items()) if k < settings.bl_sett_addr}
+        settings_dict = {k: v for k, v in list(settings.ihex.todict().items()) if k >= settings.bl_sett_addr}
         self.assertEqual(backup_dict, settings_dict)
 
     def test_generate_with_backup_page_custom_address(self):
@@ -406,7 +406,7 @@ def test_generate_with_backup_page_custom_address(self):
                           key_file=None)
 
         self.assertEqual(settings.backup_address, 0x0006F000)
-        self.assertTrue(0x0006F000 in settings.ihex.todict().keys())
+        self.assertTrue(0x0006F000 in list(settings.ihex.todict().keys()))
 
     def test_generate_with_backup_page_default_address(self):
         settings = BLDFUSettings()
@@ -424,7 +424,7 @@ def test_generate_with_backup_page_default_address(self):
                           key_file=None)
 
         self.assertEqual(settings.backup_address, (0x0006F000 - settings.bl_sett_backup_offset))
-        self.assertTrue((0x0006F000 - settings.bl_sett_backup_offset) in settings.ihex.todict().keys())
+        self.assertTrue((0x0006F000 - settings.bl_sett_backup_offset) in list(settings.ihex.todict().keys()))
 
     def test_generate_with_app_boot_validation_crc(self):
         settings = BLDFUSettings()
@@ -464,8 +464,8 @@ def test_generate_with_app_boot_validation_sha256(self):
         self.assertEqual(0x1316CFD0, settings.crc)
         self.assertEqual(0xF78E451E, settings.boot_validation_crc)
         self.assertEqual(0x02, settings.app_boot_validation_type)
-        self.assertEqual('036F52C9EBB53819D6E2B6FB57803823E864783B04D7331B46C0B5897CA9F1C7',
-                         binascii.hexlify(settings.app_boot_validation_bytes).upper())
+        self.assertEqual(bytes.fromhex('036F52C9EBB53819D6E2B6FB57803823E864783B04D7331B46C0B5897CA9F1C7'),
+                         settings.app_boot_validation_bytes)
 
     def test_generate_with_app_boot_validation_ecdsa(self):
         settings = BLDFUSettings()
@@ -525,8 +525,8 @@ def test_generate_with_sd_boot_validation_sha256(self):
         self.assertEqual(0x4637019F, settings.crc)
         self.assertEqual(0x9C761426, settings.boot_validation_crc)
         self.assertEqual(0x02, settings.sd_boot_validation_type)
-        self.assertEqual('036F52C9EBB53819D6E2B6FB57803823E864783B04D7331B46C0B5897CA9F1C7',
-                         binascii.hexlify(settings.sd_boot_validation_bytes).upper())
+        self.assertEqual(bytes.fromhex('036F52C9EBB53819D6E2B6FB57803823E864783B04D7331B46C0B5897CA9F1C7'),
+                         settings.sd_boot_validation_bytes)
 
     def test_generate_with_sd_boot_validation_ecdsa(self):
         settings = BLDFUSettings()
diff --git a/nordicsemi/dfu/tests/test_dfu_transport_serial.py b/nordicsemi/dfu/tests/test_dfu_transport_serial.py
index 33be969..fa049cf 100644
--- a/nordicsemi/dfu/tests/test_dfu_transport_serial.py
+++ b/nordicsemi/dfu/tests/test_dfu_transport_serial.py
@@ -103,7 +103,7 @@ def error_callback(log_message=""):
         self.transport.register_events_callback(DfuEvent.PROGRESS_EVENT, progress_callback)
         self.transport.register_events_callback(DfuEvent.ERROR_EVENT, error_callback())
 
-        firmware = ''
+        firmware = b''
         test_firmware_path = os.path.join("firmwares", "pca10028_nrf51422_xxac_blinky.bin")
 
         with open(test_firmware_path, 'rb') as f:
diff --git a/nordicsemi/dfu/tests/test_package.py b/nordicsemi/dfu/tests/test_package.py
index 6203a9d..18340a8 100644
--- a/nordicsemi/dfu/tests/test_package.py
+++ b/nordicsemi/dfu/tests/test_package.py
@@ -76,11 +76,11 @@ def test_generate_package_application(self):
 
             with open(os.path.join(self.work_directory, 'manifest.json'), 'r') as f:
                 _json = json.load(f)
-                self.assertEqual(u'bar.bin', _json['manifest']['application']['bin_file'])
-                self.assertEqual(u'bar.dat', _json['manifest']['application']['dat_file'])
-                self.assertTrue(u'softdevice' not in _json['manifest'])
-                self.assertTrue(u'softdevice_bootloader' not in _json['manifest'])
-                self.assertTrue(u'bootloader' not in _json['manifest'])
+                self.assertEqual('bar.bin', _json['manifest']['application']['bin_file'])
+                self.assertEqual('bar.dat', _json['manifest']['application']['dat_file'])
+                self.assertTrue('softdevice' not in _json['manifest'])
+                self.assertTrue('softdevice_bootloader' not in _json['manifest'])
+                self.assertTrue('bootloader' not in _json['manifest'])
 
     def test_generate_package_sd_bl(self):
         self.p = Package(app_version=100,
@@ -108,8 +108,8 @@ def test_generate_package_sd_bl(self):
 
             with open(os.path.join(self.work_directory, 'manifest.json'), 'r') as f:
                 _json = json.load(f)
-                self.assertEqual(u'sd_bl.bin', _json['manifest']['softdevice_bootloader']['bin_file'])
-                self.assertEqual(u'sd_bl.dat', _json['manifest']['softdevice_bootloader']['dat_file'])
+                self.assertEqual('sd_bl.bin', _json['manifest']['softdevice_bootloader']['bin_file'])
+                self.assertEqual('sd_bl.dat', _json['manifest']['softdevice_bootloader']['dat_file'])
 
     def test_unpack_package_a(self):
         self.p = Package(app_version=100,
@@ -122,7 +122,7 @@ def test_unpack_package_a(self):
         unpacked_dir = os.path.join(self.work_directory, "unpacked")
         manifest = self.p.unpack_package(os.path.join(self.work_directory, pkg_name), unpacked_dir)
         self.assertIsNotNone(manifest)
-        self.assertEqual(u'bar.bin', manifest.softdevice.bin_file)
+        self.assertEqual('bar.bin', manifest.softdevice.bin_file)
 #         self.assertEqual(0, manifest.softdevice.init_packet_data.ext_packet_id)
 #         self.assertIsNotNone(manifest.softdevice.init_packet_data.firmware_crc16)
 
@@ -137,7 +137,7 @@ def test_unpack_package_b(self):
         unpacked_dir = os.path.join(self.work_directory, "unpacked")
         manifest = self.p.unpack_package(os.path.join(self.work_directory, pkg_name), unpacked_dir)
         self.assertIsNotNone(manifest)
-        self.assertEqual(u'bar.bin', manifest.softdevice.bin_file)
+        self.assertEqual('bar.bin', manifest.softdevice.bin_file)
 
     def test_unpack_package_c(self):
         self.p = Package(app_version=100,
@@ -150,7 +150,7 @@ def test_unpack_package_c(self):
         unpacked_dir = os.path.join(self.work_directory, "unpacked")
         manifest = self.p.unpack_package(os.path.join(self.work_directory, pkg_name), unpacked_dir)
         self.assertIsNotNone(manifest)
-        self.assertEqual(u'bar.bin', manifest.softdevice.bin_file)
+        self.assertEqual('bar.bin', manifest.softdevice.bin_file)
 
 
 if __name__ == '__main__':
diff --git a/nordicsemi/dfu/tests/test_signing.py b/nordicsemi/dfu/tests/test_signing.py
index c056513..e74af27 100644
--- a/nordicsemi/dfu/tests/test_signing.py
+++ b/nordicsemi/dfu/tests/test_signing.py
@@ -44,7 +44,7 @@
 from nordicsemi.dfu.signing import Signing
 
 
-class TestSinging(unittest.TestCase):
+class TestSigning(unittest.TestCase):
     def setUp(self):
         script_abspath = os.path.abspath(__file__)
         script_dirname = os.path.dirname(script_abspath)
@@ -114,10 +114,10 @@ def test_get_sk_hex(self):
 
     def test_get_vk_pem(self):
         key_file_name = 'key.pem'
-        expected_vk_pem = "-----BEGIN PUBLIC KEY-----\n" \
-                          "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEZY2i7duYH2l9rnIg1oIXq+0/uHAF\n" \
-                          "7IoFubVru6oX9GCQm67NrXImwgS2ErZi/0/MvRsMkIQQkNg6Wc2tbJgdTA==\n" \
-                          "-----END PUBLIC KEY-----\n"
+        expected_vk_pem = b"-----BEGIN PUBLIC KEY-----\n" \
+                          b"MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEZY2i7duYH2l9rnIg1oIXq+0/uHAF\n" \
+                          b"7IoFubVru6oX9GCQm67NrXImwgS2ErZi/0/MvRsMkIQQkNg6Wc2tbJgdTA==\n" \
+                          b"-----END PUBLIC KEY-----\n"
 
         signing = Signing()
         signing.load_key(key_file_name)
diff --git a/nordicsemi/dfu/util.py b/nordicsemi/dfu/util.py
index bd9674d..8f85c5b 100644
--- a/nordicsemi/dfu/util.py
+++ b/nordicsemi/dfu/util.py
@@ -1,4 +1,4 @@
-from __future__ import print_function
+
 #
 # Copyright (c) 2016 Nordic Semiconductor ASA
 # All rights reserved.
@@ -44,7 +44,7 @@
 class NordicEnum(Enum):
   @classmethod
   def tostring(cls, val):
-    for k,v in vars(cls).iteritems():
+    for k,v in vars(cls).items():
         if v==val:
             return k
 
@@ -66,7 +66,7 @@ def query_func(question, default=False):
 
     while True:
         print("%s %s" % (question, prompt))
-        choice = raw_input().lower()
+        choice = input().lower()
         if choice == '':
             return default
         elif choice in valid:
diff --git a/nordicsemi/lister/lister_backend.py b/nordicsemi/lister/lister_backend.py
index 5194419..7d6be80 100644
--- a/nordicsemi/lister/lister_backend.py
+++ b/nordicsemi/lister/lister_backend.py
@@ -1,4 +1,3 @@
-#
 # Copyright (c) 2019 Nordic Semiconductor ASA
 # All rights reserved.
 #
@@ -33,14 +32,12 @@
 # ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#
-import abc
 
+from abc import ABC, abstractmethod
 
-class AbstractLister(object):
-    __metaclass__ = abc.ABCMeta
 
-    @abc.abstractmethod
+class AbstractLister(ABC):
+    @abstractmethod
     def enumerate(self):
         """
         Enumerate all usb devices
diff --git a/nordicsemi/lister/unix/unix_lister.py b/nordicsemi/lister/unix/unix_lister.py
index 6716d06..946d1a1 100644
--- a/nordicsemi/lister/unix/unix_lister.py
+++ b/nordicsemi/lister/unix/unix_lister.py
@@ -69,4 +69,4 @@ def enumerate(self):
             else:
                 device_identities[id] = EnumeratedDevice(vendor_id, product_id, serial_number, [com_port])
 
-        return [device for device in device_identities.values()]
+        return [device for device in list(device_identities.values())]
diff --git a/nordicsemi/lister/windows/constants.py b/nordicsemi/lister/windows/constants.py
index c63cf1b..62cf05d 100644
--- a/nordicsemi/lister/windows/constants.py
+++ b/nordicsemi/lister/windows/constants.py
@@ -23,7 +23,7 @@
 """
 
 import enum
-from structures import DevicePropertyKey
+from .structures import DevicePropertyKey
 
 
 # noinspection SpellCheckingInspection
diff --git a/nordicsemi/lister/windows/lister_win32.py b/nordicsemi/lister/windows/lister_win32.py
index bf03da1..e1d9aef 100644
--- a/nordicsemi/lister/windows/lister_win32.py
+++ b/nordicsemi/lister/windows/lister_win32.py
@@ -40,8 +40,8 @@
 from nordicsemi.lister.enumerated_device import EnumeratedDevice
 
 if sys.platform == 'win32':
-    from constants import DIGCF_PRESENT, DEVPKEY, DIGCF_DEVICEINTERFACE
-    from structures import GUID, DeviceInfoData, ctypesInternalGUID
+    from .constants import DIGCF_PRESENT, DEVPKEY, DIGCF_DEVICEINTERFACE
+    from .structures import GUID, DeviceInfoData, ctypesInternalGUID
 
     import ctypes
     from ctypes.wintypes import *
diff --git a/nordicsemi/thread/dfu_server.py b/nordicsemi/thread/dfu_server.py
index daa0729..215119b 100644
--- a/nordicsemi/thread/dfu_server.py
+++ b/nordicsemi/thread/dfu_server.py
@@ -122,7 +122,7 @@ def __init__(self):
 Resource = namedtuple('Resource', ['path', 'data'])
 
 class ThreadDfuServer():
-    REALM_LOCAL_ADDR  = ip_address(u'FF03::1')
+    REALM_LOCAL_ADDR  = ip_address('FF03::1')
 
     SPBLK_SIZE        = 64      # number of CoAP blocks of BLOCK_SZX size each
     SPBLK_UPLOAD_RATE = 1       # in blocks / seconds
@@ -370,7 +370,7 @@ def receive_request(self, request):
             ThreadDfuServer.BITMAP_URI : self._handle_bitmap_request,
         }
 
-        for uri, handler in handlers.items():
+        for uri, handler in list(handlers.items()):
             if '/'.join(request.opt.uri_path).startswith(uri):
                 return handler(request)
 
diff --git a/nordicsemi/thread/tncp.py b/nordicsemi/thread/tncp.py
index 196da0c..814bf5a 100644
--- a/nordicsemi/thread/tncp.py
+++ b/nordicsemi/thread/tncp.py
@@ -78,7 +78,7 @@ def __init__(self, port, stream_descriptor, config = None):
 
     @staticmethod
     def _propid_to_str(propid):
-        for name, value in SPINEL.__dict__.iteritems():
+        for name, value in SPINEL.__dict__.items():
             if (name.startswith('PROP_') and value == propid):
                 return name
 
@@ -160,7 +160,7 @@ def add_ip_address(self, ipaddr):
         flags = 0
         prefix_len = 64
 
-        prefix = ipaddress.IPv6Interface(unicode(ipaddr))
+        prefix = ipaddress.IPv6Interface(str(ipaddr))
         arr = prefix.ip.packed
         arr += self._wpan.encode_fields('CLLC',
                                            prefix_len,
@@ -174,7 +174,7 @@ def add_ip_address(self, ipaddr):
     def print_addresses(self):
         logger.info("NCP Thread IPv6 addresses:")
         for addr in self._wpan.get_ipaddrs():
-            logger.info(unicode(addr))
+            logger.info(str(addr))
 
     def send(self, payload, dest):
         if (dest.addr.is_multicast):
diff --git a/nordicsemi/utility/target_registry.py b/nordicsemi/utility/target_registry.py
index 6d2ea05..f567546 100644
--- a/nordicsemi/utility/target_registry.py
+++ b/nordicsemi/utility/target_registry.py
@@ -1,5 +1,4 @@
-#
-# Copyright (c) 2016 Nordic Semiconductor ASA
+# Copyright (c) 2016 - 2019 Nordic Semiconductor ASA
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without modification,
@@ -33,17 +32,15 @@
 # ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#
 
 import re
 import os
 import json
-from abc import ABCMeta, abstractmethod
 
+from abc import ABC, abstractmethod
 
-class TargetDatabase(object):
-    __metaclass__ = ABCMeta
 
+class TargetDatabase(ABC):
     @abstractmethod
     def get_targets(self):
         pass
@@ -73,7 +70,7 @@ def get_targets(self):
         if self.targets is None:
             self.targets = []
 
-            for key, value in os.environ.iteritems():
+            for key, value in os.environ.items():
                 match = re.match("NORDICSEMI_TARGET_(?P<target>\d+)_(?P<key>[a-zA-Z_]+)", key)
 
                 if match:
diff --git a/nordicsemi/version.py b/nordicsemi/version.py
index 08a20e5..6716769 100644
--- a/nordicsemi/version.py
+++ b/nordicsemi/version.py
@@ -37,4 +37,4 @@
 
 """ Version definition for nrfutil. """
 
-NRFUTIL_VERSION = "5.1.0"
+NRFUTIL_VERSION = "6.0.0a0"
diff --git a/nordicsemi/zigbee/prod_config.py b/nordicsemi/zigbee/prod_config.py
index 46f3b8d..2374fe3 100644
--- a/nordicsemi/zigbee/prod_config.py
+++ b/nordicsemi/zigbee/prod_config.py
@@ -63,7 +63,7 @@ def __init__(self, path):
             # Open the YAML file
             with open(path, 'r') as f:
                 self._yaml = yaml.load(f)
-        
+
         except yaml.YAMLError as e:
             raise ProductionConfigWrongException
 
@@ -85,21 +85,21 @@ def __init__(self, path):
                 self._parsed_values["install_code"] = str(b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
                 self._ic_crc = 0
             else:
-                self._parsed_values["install_code"] = self._yaml["install_code"].decode('hex')
+                self._parsed_values["install_code"] = bytes.fromhex(self._yaml["install_code"])
                 self._ic_crc = self._crc16(self._parsed_values["install_code"])
-            
+
             # Handle the Transmission Power
             if "tx_power" not in self._yaml:
-                self._parsed_values["tx_power"] = str(bytearray(16))
+                self._parsed_values["tx_power"] = bytes(16)
             else:
-                self._parsed_values["tx_power"] = str(bytearray([self._yaml["tx_power"]] * 16))
+                self._parsed_values["tx_power"] = bytes([self._yaml["tx_power"]] * 16)
 
             # Handle Application Data (optional)
             if "app_data" not in self._yaml:
-                self._parsed_values["app_data"] = ''
+                self._parsed_values["app_data"] = b''
                 self._ad_len = 0
             else:
-                self._parsed_values["app_data"] = self._yaml["app_data"].decode('hex')
+                self._parsed_values["app_data"] = bytes.fromhex(self._yaml["app_data"])
                 self._ad_len = len(self._parsed_values["app_data"])
 
         except (TypeError, ValueError) as e:
@@ -112,7 +112,6 @@ def _custom_crc32(self, data):
         ZB_CRC32_POLY = 0x04C11DB7
         crc = 0
         for d in data:
-            d = ord(d)
             c  = ((( crc ^ d ) & 0xff) << 24);
             for j in range(8):
                 if c & 0x80000000:
diff --git a/requirements-dev.txt b/requirements-dev.txt
new file mode 100644
index 0000000..533fe0c
--- /dev/null
+++ b/requirements-dev.txt
@@ -0,0 +1,4 @@
+-r requirements.txt
+behave
+nose
+pyinstaller
diff --git a/requirements.txt b/requirements.txt
index aac1e77..10d7f02 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,15 +1,14 @@
-six ~= 1.9
-pyserial ~= 3.0
-enum34 ~= 1.0
+antlib == 1.1b0.post0; sys_platform == 'win32'
 click ~= 7.0
-ecdsa ~= 0.13.0
-behave ~= 1.0
-protobuf ~= 3.6
-pc_ble_driver_py ~= 0.11.4
-tqdm ~= 4.25
-piccata ~= 1.0
-pyspinel == 1.0.0a3
-intelhex ~= 2.2
-pyyaml >= 4.2b1
 crcmod ~= 1.7
+ecdsa ~= 0.13.2
+intelhex ~= 2.2
 libusb1 ~= 1.7
+pc_ble_driver_py == 0.12.0
+piccata # FIXME: Specify version constraint when piccata with py3 support becomes available.
+protobuf ~= 3.8
+pyserial ~= 3.0
+pyspinel == 1.0.0a3
+pywin32 == 225; sys_platform == 'win32'
+pyyaml ~= 5.1
+tqdm ~= 4.36
diff --git a/setup.py b/setup.py
index d14f653..7fd0688 100644
--- a/setup.py
+++ b/setup.py
@@ -167,7 +167,7 @@ def run_tests(self):
 
         'License :: Other/Proprietary License',
 
-        'Programming Language :: Python :: 2.7',
+        'Programming Language :: Python :: 3.7',
     ],
     keywords = 'nordic nrf51 nrf52 ble bluetooth dfu ota softdevice serialization nrfutil pc-nrfutil',
     cmdclass={
diff --git a/tests/bdd/steps/common_steps.py b/tests/bdd/steps/common_steps.py
index 0aa8d7f..116c64b 100644
--- a/tests/bdd/steps/common_steps.py
+++ b/tests/bdd/steps/common_steps.py
@@ -35,7 +35,7 @@
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 
-from Queue import Queue
+from queue import Queue
 import logging
 import os
 import subprocess
diff --git a/tests/bdd/steps/dfu_steps.py b/tests/bdd/steps/dfu_steps.py
index b90ceb0..c5ec833 100644
--- a/tests/bdd/steps/dfu_steps.py
+++ b/tests/bdd/steps/dfu_steps.py
@@ -35,7 +35,7 @@
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 
-from Queue import Empty
+from queue import Empty
 import logging
 import os
 import time
@@ -188,7 +188,7 @@ def program_image_ble(nrfjprog, full_image_path, snr):
 
 STDOUT_TEXT_WAIT_TIME = 50  # Number of seconds to wait for expected output from stdout
 
-@given(u'the user wants to perform dfu {dfu_type}')
+@given('the user wants to perform dfu {dfu_type}')
 def step_impl(context, dfu_type):
     runner = CliRunner()
     context.runner = runner
@@ -196,17 +196,17 @@ def step_impl(context, dfu_type):
 
     context.args = args
 
-@given(u'using package {package}')
+@given('using package {package}')
 def step_impl(context, package):
     full_package_path = resolve_hex_path(package)
     context.args.extend(['-pkg', full_package_path])
     context.pkg = full_package_path
 
-@given(u'option {args}')
+@given('option {args}')
 def step_impl(context, args):
     context.args.extend(args.split(" "))
 
-@given(u'-snr {device}')
+@given('-snr {device}')
 def step_impl(context, device):
     assert device in os.environ, \
     "Environment variable '{}' must be exported with device serial number".format(device)
@@ -214,7 +214,7 @@ def step_impl(context, device):
     snr = str(os.environ[device])
     context.args.extend(["-snr", snr])
 
-@given(u'nrfjprog {image} for {image_type} {board}')
+@given('nrfjprog {image} for {image_type} {board}')
 def step_impl(context, image, image_type, board):
 
     full_image_path = resolve_hex_path(image)
@@ -246,7 +246,7 @@ def step_impl(context, image, image_type, board):
 
 
 
-@then(u'perform dfu')
+@then('perform dfu')
 def step_impl(context):
     result = context.runner.invoke(cli, context.args)
     logger.debug("exit_code: %s, output: \'%s\'", result.exit_code, result.output)
diff --git a/tests/bdd/steps/genpkg_generate_dfu_package_steps.py b/tests/bdd/steps/genpkg_generate_dfu_package_steps.py
index b777dc9..bcc1c3a 100644
--- a/tests/bdd/steps/genpkg_generate_dfu_package_steps.py
+++ b/tests/bdd/steps/genpkg_generate_dfu_package_steps.py
@@ -48,25 +48,25 @@
 logger = logging.getLogger(__file__)
 
 
-@given(u'the user wants to generate a DFU package with application {application}, bootloader {bootloader} and SoftDevice {softdevice} with name {package}')
+@given('the user wants to generate a DFU package with application {application}, bootloader {bootloader} and SoftDevice {softdevice} with name {package}')
 def step_impl(context, application, bootloader, softdevice, package):
     runner = CliRunner()
     context.runner = runner
     args = ['dfu', 'genpkg']
 
-    if application != u'not_set':
+    if application != 'not_set':
         args.extend(['--application', os.path.join(get_resources_path(), application)])
         context.application = application
     else:
         context.application = None
 
-    if bootloader != u'not_set':
+    if bootloader != 'not_set':
         args.extend(['--bootloader', os.path.join(get_resources_path(), bootloader)])
         context.bootloader = bootloader
     else:
         context.bootloader = None
 
-    if softdevice != u'not_set':
+    if softdevice != 'not_set':
         args.extend(['--softdevice', os.path.join(get_resources_path(), softdevice)])
         context.softdevice = softdevice
     else:
@@ -77,52 +77,52 @@ def step_impl(context, application, bootloader, softdevice, package):
     context.args = args
 
 
-@given(u'with option --application-version {app_ver}')
+@given('with option --application-version {app_ver}')
 def step_impl(context, app_ver):
     context.application_version = None
 
-    if app_ver == u'not_set':
+    if app_ver == 'not_set':
         context.application_version = 0xFFFFFFFF
-    elif app_ver == u'none':
+    elif app_ver == 'none':
         context.args.extend(['--application-version', 'None'])
     else:
         context.args.extend(['--application-version', app_ver])
         context.application_version = int_as_text_to_int(app_ver)
 
 
-@given(u'with option --dev-revision {dev_rev}')
+@given('with option --dev-revision {dev_rev}')
 def step_impl(context, dev_rev):
     context.dev_revision = None
 
-    if dev_rev == u'not_set':
+    if dev_rev == 'not_set':
         context.dev_revision = 0xFFFF
-    elif dev_rev == u'none':
+    elif dev_rev == 'none':
         context.args.extend(['--dev-revision', 'None'])
     else:
         context.args.extend(['--dev-revision', dev_rev])
         context.dev_revision = int_as_text_to_int(dev_rev)
 
 
-@given(u'with option --dev-type {dev_type}')
+@given('with option --dev-type {dev_type}')
 def step_impl(context, dev_type):
     context.dev_type = None
 
-    if dev_type == u'not_set':
+    if dev_type == 'not_set':
         context.dev_type = 0xFFFF
-    elif dev_type == u'none':
+    elif dev_type == 'none':
         context.args.extend(['--dev-type', 'None'])
     else:
         context.args.extend(['--dev-type', dev_type])
         context.dev_type = int_as_text_to_int(dev_type)
 
 
-@given(u'with option --dfu-ver {dfu_ver}')
+@given('with option --dfu-ver {dfu_ver}')
 def step_impl(context, dfu_ver):
     context.firmware_hash = None
     context.ext_packet_id = None
     context.init_packet_ecds = None
 
-    if dfu_ver == u'not_set':
+    if dfu_ver == 'not_set':
         context.dfu_ver = 0.5
         context.ext_packet_id = 0
     else:
@@ -142,13 +142,13 @@ def step_impl(context, dfu_ver):
         context.dfu_ver = float(dfu_ver)
 
 
-@given(u'with option --sd-req {sd_reqs}')
+@given('with option --sd-req {sd_reqs}')
 def step_impl(context, sd_reqs):
     context.sd_req = None
 
-    if sd_reqs == u'not_set':
+    if sd_reqs == 'not_set':
         context.sd_req = [0xFFFE]
-    elif sd_reqs == u'none':
+    elif sd_reqs == 'none':
         context.args.extend(['--sd-req', 'None'])
     else:
         context.args.extend(['--sd-req', sd_reqs])
@@ -162,19 +162,19 @@ def step_impl(context, sd_reqs):
         context.sd_req = sd_reqs_value
 
 
-@given(u'with option --key-file {pem_file}')
+@given('with option --key-file {pem_file}')
 def step_impl(context, pem_file):
-    if pem_file != u'not_set':
+    if pem_file != 'not_set':
         context.args.extend(['--key-file', os.path.join(get_resources_path(), pem_file)])
         context.dfu_ver = 0.8
 
 
-@when(u'user press enter')
+@when('user press enter')
 def step_impl(context):
     pass
 
 
-@then(u'the generated DFU package {package} contains correct data')
+@then('the generated DFU package {package} contains correct data')
 def step_impl(context, package):
     with context.runner.isolated_filesystem():
         pkg_full_name = os.path.join(os.getcwd(), package)
diff --git a/tests/bdd/steps/help_information_steps.py b/tests/bdd/steps/help_information_steps.py
index a34da48..6cedc8a 100644
--- a/tests/bdd/steps/help_information_steps.py
+++ b/tests/bdd/steps/help_information_steps.py
@@ -35,7 +35,7 @@
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 
-from Queue import Empty
+from queue import Empty
 import logging
 import os
 import time
@@ -52,7 +52,7 @@
 STDOUT_TEXT_WAIT_TIME = 50  # Number of seconds to wait for expected output from stdout
 
 
-@given(u'user types \'{command}\'')
+@given('user types \'{command}\'')
 def step_impl(context, command):
     args = command.split(' ')
     assert args[0] == 'nrfutil'
@@ -64,7 +64,7 @@ def step_impl(context, command):
     context.args = exec_args
 
 
-@then(u'output contains \'{stdout_text}\' and exit code is {exit_code}')
+@then('output contains \'{stdout_text}\' and exit code is {exit_code}')
 def step_impl(context, stdout_text, exit_code):
     result = context.runner.invoke(cli, context.args)
     logger.debug("exit_code: %s, output: \'%s\'", result.exit_code, result.output)
@@ -72,7 +72,7 @@ def step_impl(context, stdout_text, exit_code):
     assert result.output != None
     assert result.output.find(stdout_text) >= 0
 
-@then(u'output version is correct')
+@then('output version is correct')
 def step_impl(context):
     assert "nrfutil_version" in os.environ, \
     "Environment variable 'nrfutil_version' must be exported"
diff --git a/tests/bdd/steps/util.py b/tests/bdd/steps/util.py
index 3a67e9e..eb5eff4 100644
--- a/tests/bdd/steps/util.py
+++ b/tests/bdd/steps/util.py
@@ -79,7 +79,7 @@ def generate_options_table_for_cucumber():
     number_of_optional_option_permutations *= int(math.pow(3, number_of_3_option_options))
     number_of_optional_option_permutations *= int(math.pow(4, number_of_4_option_options))
 
-    for x in xrange(0, number_of_optional_option_permutations):
+    for x in range(0, number_of_optional_option_permutations):
         retval += "{0:<8}".format(" ")
         retval += "| {0:<12}| {1:<29}| {2:<29}|".format("blinky.bin", "not_set", "not_set")
 
@@ -144,7 +144,7 @@ def generate_options_table_for_cucumber():
         if option == 2:
             sd_reqs = []
 
-            for i in xrange(0, randint(1, 4)):
+            for i in range(0, randint(1, 4)):
                 sd_reqs.append("0x{0:04x}".format(randint(0, 65535)))
 
             retval += " {0:<28}|".format(",".join(sd_reqs))
diff --git a/tests/protobuf/__main__.py b/tests/protobuf/__main__.py
index 98932b4..74b03bb 100644
--- a/tests/protobuf/__main__.py
+++ b/tests/protobuf/__main__.py
@@ -20,7 +20,7 @@ def test_construct_from_empty_string(self):
         empty buffer
         """
 
-        self.assertRaisesRegexp(
+        self.assertRaisesRegex(
             RuntimeError,
             "app_size is not set. It must be set when type is APPLICATION",
             InitPacketPB,
diff --git a/tests/test_cli.py b/tests/test_cli.py
index bef6134..bee4220 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -41,7 +41,6 @@ def test_dfu_ble_address(self):
         address = 'AABBCC11223'
         result = self.runner.invoke(self.cli, argumentList + [address])
         self.assertTrue('Invalid address' in result.output)
-        print(result.exception)
         self.assertIsNone(result.exception)
 
         address = 'AABBCC1122334'