diff --git a/.gitignore b/.gitignore
index 55683e9..11614af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,115 @@
-/build/
-/dist/
-/docs/_*
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
 *.egg-info/
-*.py[co]
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+.hypothesis/
+.pytest_cache/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+.python-version
+
+# celery beat schedule file
+celerybeat-schedule
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
diff --git a/.travis.yml b/.travis.yml
index 3d3f7ae..1987055 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,7 @@ language: python
 python:
     # - 2.6 disabled as the TestLoader.discover() method is not available on python < 2.7
     - 2.7
+    - 3.6
     - pypy
 
 matrix:
diff --git a/docs/index.rst b/docs/index.rst
index 63e73f9..0ff804a 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -109,7 +109,7 @@ You may control the browser's policy by using the methods of
 
     # Sometimes it's useful to process bad headers or bad HTML:
     response = br.response()  # this is a copy of response
-    headers = response.info()  # currently, this is a mimetools.Message
+    headers = response.info()  # currently, this is a email.mime.message.MIMEMessage
     headers["Content-type"] = "text/html; charset=utf-8"
     response.set_data(response.get_data().replace("<!---", "<!--"))
     br.set_response(response)
diff --git a/mechanize/__init__.py b/mechanize/__init__.py
index 8e7e7a2..c8f35a0 100644
--- a/mechanize/__init__.py
+++ b/mechanize/__init__.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 
 import logging
 
diff --git a/mechanize/_auth.py b/mechanize/_auth.py
index 7fbccc3..70aae0f 100644
--- a/mechanize/_auth.py
+++ b/mechanize/_auth.py
@@ -9,7 +9,7 @@
 
 """
 
-from __future__ import absolute_import
+
 from ._urllib2_fork import HTTPPasswordMgr
 from .polyglot import is_string, iteritems
 
diff --git a/mechanize/_clientcookie.py b/mechanize/_clientcookie.py
index 4eb6fb4..8c0243a 100644
--- a/mechanize/_clientcookie.py
+++ b/mechanize/_clientcookie.py
@@ -1,5 +1,3 @@
-from __future__ import absolute_import
-
 import re
 import time
 from .polyglot import (
@@ -17,6 +15,10 @@
 ]
 
 
+def cmp(a, b):
+    return (a > b) - (a < b)
+
+
 def effective_request_host(request):
     """Return the effective request-host, as defined by RFC 2965."""
     return eff_request_host(request)[1]
diff --git a/mechanize/_debug.py b/mechanize/_debug.py
index 4bb1c7c..f58dc20 100644
--- a/mechanize/_debug.py
+++ b/mechanize/_debug.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 
 import logging
 
diff --git a/mechanize/_entities.py b/mechanize/_entities.py
index c051c81..70badfc 100644
--- a/mechanize/_entities.py
+++ b/mechanize/_entities.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 # vim:fileencoding=utf-8
 # License: BSD Copyright: 2017, Kovid Goyal <kovid at kovidgoyal.net>
 
@@ -16,7 +16,7 @@
     'acute': '´',
     'acy': 'а',
     'aelig': 'æ',
-    'af': '\u2061',
+    'af': '\\u2061',
     'afr': '𝔞',
     'agrave': 'à',
     'alefsym': 'ℵ',
@@ -55,7 +55,7 @@
     'ape': '≊',
     'apid': '≋',
     'apos': "'",
-    'applyfunction': '\u2061',
+    'applyfunction': '\\u2061',
     'approx': '≈',
     'approxeq': '≊',
     'aring': 'å',
@@ -390,11 +390,11 @@
     'emptysmallsquare': '◻',
     'emptyv': '∅',
     'emptyverysmallsquare': '▫',
-    'emsp': '\u2003',
-    'emsp13': '\u2004',
-    'emsp14': '\u2005',
+    'emsp': '\\u2003',
+    'emsp13': '\\u2004',
+    'emsp14': '\\u2005',
     'eng': 'ŋ',
-    'ensp': '\u2002',
+    'ensp': '\\u2002',
     'eogon': 'ę',
     'eopf': '𝕖',
     'epar': '⋕',
@@ -534,7 +534,7 @@
     'gvertneqq': '≩︀',
     'gvne': '≩︀',
     'hacek': 'ˇ',
-    'hairsp': '\u200a',
+    'hairsp': '\\u200a',
     'half': '½',
     'hamilt': 'ℋ',
     'hardcy': 'ъ',
@@ -567,7 +567,7 @@
     'hybull': '⁃',
     'hyphen': '‐',
     'iacute': 'í',
-    'ic': '\u2063',
+    'ic': '\\u2063',
     'icirc': 'î',
     'icy': 'и',
     'idot': 'İ',
@@ -605,8 +605,8 @@
     'intersection': '⋂',
     'intlarhk': '⨗',
     'intprod': '⨼',
-    'invisiblecomma': '\u2063',
-    'invisibletimes': '\u2062',
+    'invisiblecomma': '\\u2063',
+    'invisibletimes': '\\u2062',
     'iocy': 'ё',
     'iogon': 'į',
     'iopf': '𝕚',
@@ -620,7 +620,7 @@
     'isins': '⋴',
     'isinsv': '⋳',
     'isinv': '∈',
-    'it': '\u2062',
+    'it': '\\u2062',
     'itilde': 'ĩ',
     'iukcy': 'і',
     'iuml': 'ï',
@@ -792,7 +792,7 @@
     'lrcorner': '⌟',
     'lrhar': '⇋',
     'lrhard': '⥭',
-    'lrm': '\u200e',
+    'lrm': '\\u200e',
     'lrtri': '⊿',
     'lsaquo': '‹',
     'lscr': '𝓁',
@@ -835,7 +835,7 @@
     'mdash': '—',
     'mddot': '∺',
     'measuredangle': '∡',
-    'mediumspace': '\u205f',
+    'mediumspace': '\\u205f',
     'mellintrf': 'ℳ',
     'mfr': '𝔪',
     'mho': '℧',
@@ -887,10 +887,10 @@
     'nearr': '↗',
     'nearrow': '↗',
     'nedot': '≐̸',
-    'negativemediumspace': '\u200b',
-    'negativethickspace': '\u200b',
-    'negativethinspace': '\u200b',
-    'negativeverythinspace': '\u200b',
+    'negativemediumspace': '\\u200b',
+    'negativethickspace': '\\u200b',
+    'negativethinspace': '\\u200b',
+    'negativeverythinspace': '\\u200b',
     'nequiv': '≢',
     'nesear': '⤨',
     'nesim': '≂̸',
@@ -934,7 +934,7 @@
     'nltrie': '⋬',
     'nltv': '≪̸',
     'nmid': '∤',
-    'nobreak': '\u2060',
+    'nobreak': '\\u2060',
     'nonbreakingspace': '\xa0',
     'nopf': '𝕟',
     'not': '¬',
@@ -1050,7 +1050,7 @@
     'nu': 'ν',
     'num': '#',
     'numero': '№',
-    'numsp': '\u2007',
+    'numsp': '\\u2007',
     'nvap': '≍⃒',
     'nvdash': '⊬',
     'nvge': '≥⃒',
@@ -1201,7 +1201,7 @@
     'prurel': '⊰',
     'pscr': '𝓅',
     'psi': 'ψ',
-    'puncsp': '\u2008',
+    'puncsp': '\\u2008',
     'qfr': '𝔮',
     'qint': '⨌',
     'qopf': '𝕢',
@@ -1307,7 +1307,7 @@
     'risingdotseq': '≓',
     'rlarr': '⇄',
     'rlhar': '⇌',
-    'rlm': '\u200f',
+    'rlm': '\\u200f',
     'rmoust': '⎱',
     'rmoustache': '⎱',
     'rnmid': '⫮',
@@ -1521,9 +1521,9 @@
     'thetav': 'ϑ',
     'thickapprox': '≈',
     'thicksim': '∼',
-    'thickspace': '\u205f\u200a',
-    'thinsp': '\u2009',
-    'thinspace': '\u2009',
+    'thickspace': '\\u205f\\u200a',
+    'thinsp': '\\u2009',
+    'thinspace': '\\u2009',
     'thkap': '≈',
     'thksim': '∼',
     'thorn': 'þ',
@@ -1659,7 +1659,7 @@
     'verticalline': '|',
     'verticalseparator': '❘',
     'verticaltilde': '≀',
-    'verythinspace': '\u200a',
+    'verythinspace': '\\u200a',
     'vfr': '𝔳',
     'vltri': '⊲',
     'vnsub': '⊂⃒',
@@ -1720,15 +1720,15 @@
     'zcy': 'з',
     'zdot': 'ż',
     'zeetrf': 'ℨ',
-    'zerowidthspace': '\u200b',
+    'zerowidthspace': '\\u200b',
     'zeta': 'ζ',
     'zfr': '𝔷',
     'zhcy': 'ж',
     'zigrarr': '⇝',
     'zopf': '𝕫',
     'zscr': '𝓏',
-    'zwj': '\u200d',
-    'zwnj': '\u200c',
+    'zwj': '\\u200d',
+    'zwnj': '\\u200c',
 # }}}
 }
 
diff --git a/mechanize/_equiv.py b/mechanize/_equiv.py
index 289b5a0..18a094e 100644
--- a/mechanize/_equiv.py
+++ b/mechanize/_equiv.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 # vim:fileencoding=utf-8
 # License: BSD Copyright: 2017, Kovid Goyal <kovid at kovidgoyal.net>
 
@@ -11,7 +11,7 @@
 from ._entities import html5_entities
 from .polyglot import codepoint_to_chr
 
-space_chars = frozenset(("\t", "\n", "\u000C", " ", "\r"))
+space_chars = frozenset(("\t", "\n", "\\u000C", " ", "\r"))
 space_chars_bytes = frozenset(item.encode("ascii") for item in space_chars)
 ascii_letters_bytes = frozenset(
     item.encode("ascii") for item in string.ascii_letters)
@@ -75,7 +75,7 @@ def __next__(self):
             raise TypeError
         return self[p:p + 1]
 
-    def next(self):
+    def __next__(self):
         # Py2 compat
         return self.__next__()
 
diff --git a/mechanize/_form.py b/mechanize/_form.py
index 31922ee..a9696de 100644
--- a/mechanize/_form.py
+++ b/mechanize/_form.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 
 import re
 from collections import defaultdict
@@ -13,7 +13,7 @@ class SkipControl(ValueError):
 
 
 def normalize_line_endings(text):
-    return re.sub(ur"(?:(?<!\r)\n)|(?:\r(?!\n))", u"\r\n", text)
+    return re.sub(r"(?:(?<!\r)\n)|(?:\r(?!\n))", "\r\n", text)
 
 
 def label_text(elem):
@@ -66,7 +66,7 @@ def parse_option(elem, parent_of, attrs_map):
 def parse_textarea(elem, parent_of, *a):
     ctype, name, attrs = parse_control(elem, parent_of)
     ctype = 'textarea'
-    attrs['value'] = normalize_line_endings(elem.text or u'')
+    attrs['value'] = normalize_line_endings(elem.text or '')
     return ctype, name, attrs
 
 
diff --git a/mechanize/_form_controls.py b/mechanize/_form_controls.py
index 0694e77..439e67d 100644
--- a/mechanize/_form_controls.py
+++ b/mechanize/_form_controls.py
@@ -1,6 +1,6 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 # vim:fileencoding=utf-8
-from __future__ import absolute_import
+
 
 import random
 import re
@@ -12,7 +12,7 @@
 from .polyglot import urlparse, urlunparse, urlencode, is_py2, iteritems
 
 if is_py2:
-    from cStringIO import StringIO
+    from io import StringIO
 else:
     from io import StringIO  # 2to3: probably broken when writing bytes
 
diff --git a/mechanize/_gzip.py b/mechanize/_gzip.py
index 0502eec..39686db 100644
--- a/mechanize/_gzip.py
+++ b/mechanize/_gzip.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 
 import struct
 import zlib
@@ -10,7 +10,7 @@
 
 CRC_MASK = 0xffffffff
 if is_py2:
-    CRC_MASK = long(CRC_MASK)
+    CRC_MASK = int(CRC_MASK)
 
 
 def gzip_prefix():
@@ -141,7 +141,7 @@ def __iter__(self):
         if ans:
             yield ans
 
-    def next(self):
+    def __next__(self):
         ans = self.readline()
         if not ans:
             raise StopIteration()
@@ -191,7 +191,7 @@ def http_request(self, request):
             if sum('gzip' in x for x in existing) < 1:
                 existing.append('gzip')
                 request.add_header("Accept-Encoding",
-                                   ', '.join(filter(None, existing)))
+                                   ', '.join([_f for _f in existing if _f]))
         return request
 
     def http_response(self, request, response):
diff --git a/mechanize/_headersutil.py b/mechanize/_headersutil.py
index f57b824..77532b8 100644
--- a/mechanize/_headersutil.py
+++ b/mechanize/_headersutil.py
@@ -9,17 +9,15 @@
 
 """
 
-from __future__ import absolute_import
+
 
 import os
 import re
-from types import StringType, UnicodeType
+from six import string_types
 
 from . import _rfc3986
 from ._util import http2time
 
-STRING_TYPES = StringType, UnicodeType
-
 
 def is_html_file_extension(url, allow_xhtml):
     ext = os.path.splitext(_rfc3986.urlsplit(url)[2])[1]
@@ -111,7 +109,7 @@ def split_header_words(header_values):
     [[('Basic', None), ('realm', '"foobar"')]]
 
     """
-    assert type(header_values) not in STRING_TYPES
+    assert type(header_values) not in string_types
     result = []
     for text in header_values:
         orig_text = text
diff --git a/mechanize/_html.py b/mechanize/_html.py
index 4e91bd2..d2ebf56 100644
--- a/mechanize/_html.py
+++ b/mechanize/_html.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 
 import codecs
 import copy
@@ -35,8 +35,8 @@ def iterlinks(root, base_url):
             if val:
                 url = clean_url(val)
                 yield Link(base_url, url,
-                           compress_whitespace(u''.join(elem_text(tag))), q,
-                           tag.items())
+                           compress_whitespace(''.join(elem_text(tag))), q,
+                           list(tag.items()))
         elif q == 'base':
             href = tag.get('href')
             if href:
@@ -51,8 +51,8 @@ def get_encoding_from_response(response, verify=True):
     # HTTPEquivProcessor may be in use, so both HTTP and HTTP-EQUIV
     # headers may be in the response.  HTTP-EQUIV headers come last,
     # so try in order from first to last.
-    if response:
-        for ct in response.info().getheaders("content-type"):
+    if response and response.info().get('content-type'):
+        for ct in response.info().get_all("content-type"):
             for k, v in split_header_words([ct])[0]:
                 if k == "charset":
                     if not verify:
@@ -77,7 +77,7 @@ def __init__(self, allow_xhtml):
         self._allow_xhtml = allow_xhtml
 
     def is_html(self, response, encoding):
-        ct_hdrs = response.info().getheaders("content-type")
+        ct_hdrs = response.info().get_all("content-type")
         url = response.geturl()
         # XXX encoding
         return _is_html(ct_hdrs, url, self._allow_xhtml)
@@ -258,7 +258,7 @@ def title(self):
         if self._current_title is lazy:
             self._current_title = get_title(
                 self.root) if self.root is not None else None
-        return self._current_title or u''
+        return self._current_title or ''
 
     @property
     def global_form(self):
diff --git a/mechanize/_http.py b/mechanize/_http.py
index 21bacd0..032b2f6 100644
--- a/mechanize/_http.py
+++ b/mechanize/_http.py
@@ -1,3 +1,5 @@
+from __future__ import unicode_literals
+
 """HTTP related handlers.
 
 Note that some other HTTP handlers live in more specific modules: _auth.py,
@@ -12,7 +14,7 @@
 
 """
 
-from __future__ import absolute_import
+
 
 import logging
 import socket
@@ -176,7 +178,8 @@ def http_request(self, request):
                 request,
                 request.get_full_url(),
                 403, msg,
-                self.http_response_class(BytesIO()), BytesIO(msg))
+                self.http_response_class(
+                    BytesIO()), BytesIO(msg.encode('utf-8')))
 
     https_request = http_request
 
diff --git a/mechanize/_mechanize.py b/mechanize/_mechanize.py
index ce2d696..f8fd1fc 100644
--- a/mechanize/_mechanize.py
+++ b/mechanize/_mechanize.py
@@ -8,7 +8,7 @@
 included with the distribution).
 
 """
-from __future__ import absolute_import
+
 
 import copy
 import os
diff --git a/mechanize/_opener.py b/mechanize/_opener.py
index f2534b2..74e176d 100644
--- a/mechanize/_opener.py
+++ b/mechanize/_opener.py
@@ -8,7 +8,7 @@
 
 """
 
-from __future__ import absolute_import
+
 
 import bisect
 import os
diff --git a/mechanize/_request.py b/mechanize/_request.py
index 01c2f29..47aa692 100644
--- a/mechanize/_request.py
+++ b/mechanize/_request.py
@@ -8,7 +8,7 @@
 
 """
 
-from __future__ import absolute_import
+
 import logging
 
 from . import _rfc3986
diff --git a/mechanize/_response.py b/mechanize/_response.py
index 3f905b4..cfc54a3 100644
--- a/mechanize/_response.py
+++ b/mechanize/_response.py
@@ -1,3 +1,5 @@
+from __future__ import unicode_literals
+
 """Response classes.
 
 The seek_wrapper code is not used if you're using UserAgent with
@@ -16,10 +18,10 @@
 
 """
 
-from __future__ import absolute_import
+
 from functools import partial
 import copy
-import mimetools
+from email.message import Message
 from io import BytesIO
 
 from ._headersutil import normalize_header_name
@@ -474,7 +476,10 @@ def make_response(data, headers, url, code, msg):
 
     """
     mime_headers = make_headers(headers)
-    r = closeable_response(BytesIO(data), mime_headers, url, code, msg)
+    z = data.encode('utf-8')
+    r = closeable_response(
+        BytesIO(data.encode('utf-8')),
+        mime_headers, url, code, msg)
     return response_seek_wrapper(r)
 
 
@@ -485,7 +490,8 @@ def make_headers(headers):
     hdr_text = []
     for name_value in headers:
         hdr_text.append("%s: %s" % name_value)
-    return mimetools.Message(BytesIO("\n".join(hdr_text)))
+    s = "\n".join(hdr_text)
+    return Message(BytesIO(s.encode('utf-8')))
 
 
 # Rest of this module is especially horrible, but needed, at least until fork
diff --git a/mechanize/_rfc3986.py b/mechanize/_rfc3986.py
index 1767aca..caca677 100644
--- a/mechanize/_rfc3986.py
+++ b/mechanize/_rfc3986.py
@@ -12,10 +12,10 @@
 
 # XXX Wow, this is ugly.  Overly-direct translation of the RFC ATM.
 
-from __future__ import absolute_import
+
 import re
 
-from .polyglot import quote
+from .polyglot import quote, is_py2
 # def chr_range(a, b):
 # return "".join(map(chr, range(ord(a), ord(b)+1)))
 
@@ -38,13 +38,13 @@ def clean_url(url, encoding='utf-8'):
     # - Mozilla/Firefox will send you latin-1 if there's no non latin-1
     # characters in your link. It will send you utf-8 however if there are...
     is_unicode = not isinstance(url, bytes)
-    if not is_unicode:
+    if is_py2 and not is_unicode:
         url = url.decode(encoding, "replace")
     url = url.strip()
     # for second param to urllib.quote(), we want URI_CHARS, minus the
     # 'always_safe' characters that urllib.quote() never percent-encodes
     ans = quote(url.encode(encoding), "!*'();:@&=+$,/?%#[]~")
-    if is_unicode:
+    if is_py2 and is_unicode:
         ans = ans.decode(encoding)
     return ans
 
diff --git a/mechanize/_sockettimeout.py b/mechanize/_sockettimeout.py
index 8c7c5ba..4b42cf5 100644
--- a/mechanize/_sockettimeout.py
+++ b/mechanize/_sockettimeout.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 import socket
 
 try:
diff --git a/mechanize/_testcase.py b/mechanize/_testcase.py
index eb1c356..27ec3cc 100644
--- a/mechanize/_testcase.py
+++ b/mechanize/_testcase.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 import os
 import shutil
 import tempfile
diff --git a/mechanize/_urllib2.py b/mechanize/_urllib2.py
index a0bac95..09d317b 100644
--- a/mechanize/_urllib2.py
+++ b/mechanize/_urllib2.py
@@ -1,4 +1,4 @@
-from __future__ import absolute_import
+
 # urllib2 work-alike interface
 # ...from urllib2...
 from .polyglot import HTTPError, URLError
diff --git a/mechanize/_urllib2_fork.py b/mechanize/_urllib2_fork.py
index 099d291..fcc0e91 100644
--- a/mechanize/_urllib2_fork.py
+++ b/mechanize/_urllib2_fork.py
@@ -28,14 +28,14 @@
 # complex proxies  XXX not sure what exactly was meant by this
 # abstract factory for opener
 
-from __future__ import absolute_import
+
 
 import base64
 import bisect
 import copy
 import hashlib
 import logging
-import mimetools
+from email.message import Message
 import os
 import platform
 import posixpath
@@ -46,21 +46,37 @@
 import time
 from functools import partial
 # support for FileHandler, proxies via environment variables
-from urllib import (addinfourl, ftpwrapper, getproxies, splitattr, splitpasswd,
-                    splitport, splittype, splituser, splitvalue, unquote,
-                    unwrap, url2pathname, proxy_bypass as urllib_proxy_bypass,
-                    splithost as urllib_splithost)
 
-from . import _rfc3986
+try:
+    from urllib.request import (
+        addinfourl, ftpwrapper, getproxies, splitattr, splitpasswd,
+        splitport, splittype, splituser, splitvalue, unquote,
+        unwrap, url2pathname, proxy_bypass as urllib_proxy_bypass,
+        splithost as urllib_splithost
+    )
+except ImportError:
+    from urllib import (
+        addinfourl, ftpwrapper, getproxies, splitattr, splitpasswd,
+        splitport, splittype, splituser, splitvalue, unquote,
+        unwrap, url2pathname, proxy_bypass as urllib_proxy_bypass,
+        splithost as urllib_splithost
+    )
+
+from mechanize import _rfc3986
 from ._clientcookie import CookieJar
 from ._response import closeable_response
 from ._headersutil import normalize_header_name
 from .polyglot import (
         HTTPError, URLError, HTTPConnection, HTTPSConnection, urlparse,
         urlsplit, is_class, iteritems, is_string, raise_with_traceback,
-        StringIO, map
+        StringIO
 )
 
+try:
+    from .polyglot import map
+except ImportError:
+    pass
+
 
 def sha1_digest(bytes):
     return hashlib.sha1(bytes).hexdigest()
@@ -1112,7 +1128,8 @@ def do_open(self, http_class, req):
         http_class must implement the HTTPConnection API from httplib.
         The addinfourl return value is a file-like object.  It also
         has methods and attributes including:
-            - info(): return a mimetools.Message object for the headers
+            - info(): return a email.message.Message object
+              for the headers
             - geturl(): return the original request URL
             - code: HTTP status code
         """
@@ -1352,7 +1369,7 @@ def open_local_file(self, req):
             size = stats.st_size
             modified = emailutils.formatdate(stats.st_mtime, usegmt=True)
             mtype = mimetypes.guess_type(file)[0]
-            headers = mimetools.Message(StringIO(
+            headers = Message(StringIO(
                 'Content-type: %s\nContent-length: %d\nLast-modified: %s\n' %
                 (mtype or 'text/plain', size, modified)))
             if host:
@@ -1418,7 +1435,7 @@ def ftp_open(self, req):
             if retrlen is not None and retrlen >= 0:
                 headers += "Content-length: %d\n" % retrlen
             sf = StringIO(headers)
-            headers = mimetools.Message(sf)
+            headers = Message(sf)
             return addinfourl(fp, headers, req.get_full_url())
         except ftplib.all_errors as msg:
             raise_with_traceback(URLError('ftp error: %s' % msg))
diff --git a/mechanize/_useragent.py b/mechanize/_useragent.py
index 13daab7..f503c86 100644
--- a/mechanize/_useragent.py
+++ b/mechanize/_useragent.py
@@ -11,7 +11,7 @@
 
 """
 
-from __future__ import absolute_import
+
 
 import copy
 
diff --git a/mechanize/_util.py b/mechanize/_util.py
index ace2175..1bd7dc3 100644
--- a/mechanize/_util.py
+++ b/mechanize/_util.py
@@ -7,7 +7,7 @@
 COPYING.txt included with the distribution).
 """
 
-from __future__ import absolute_import
+
 
 import re
 import time
diff --git a/mechanize/polyglot.py b/mechanize/polyglot.py
index 1a26171..0638cdb 100644
--- a/mechanize/polyglot.py
+++ b/mechanize/polyglot.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 # vim:fileencoding=utf-8
 # License: GPLv3 Copyright: 2018, Kovid Goyal <kovid at kovidgoyal.net>
 
@@ -10,42 +10,41 @@
 is_py2 = sys.version_info.major < 3
 
 if is_py2:
-    import types
     from urllib import (
             urlencode, pathname2url, quote, addinfourl, quote_plus, urlopen
     )
     from urllib2 import (
             HTTPError, URLError, install_opener, build_opener, ProxyHandler
     )
-    from robotparser import RobotFileParser
-    from urlparse import urlsplit, urljoin, urlparse, urlunparse
-    from httplib import HTTPMessage, HTTPConnection, HTTPSConnection
-    from cookielib import (
+    from urllib.robotparser import RobotFileParser
+    from urllib.parse import urlsplit, urljoin, urlparse, urlunparse
+    from http.client import HTTPMessage, HTTPConnection, HTTPSConnection
+    from http.cookiejar import (
             DEFAULT_HTTP_PORT, CookiePolicy, DefaultCookiePolicy,
             FileCookieJar, LoadError, LWPCookieJar, _debug, domain_match,
             eff_request_host, escape_path, is_HDN, lwp_cookie_str, reach,
             request_path, request_port, user_domain_match, Cookie, CookieJar,
             MozillaCookieJar, request_host)
-    from cStringIO import StringIO
+    from io import StringIO
     from future_builtins import map  # noqa
 
     def is_string(x):
-        return isinstance(x, basestring)
+        return isinstance(x, str)
 
     def iteritems(x):
-        return x.iteritems()
+        return iter(x.items())
 
     def itervalues(x):
-        return x.itervalues()
+        return iter(x.values())
 
     def is_class(obj):
-        return isinstance(obj, (types.ClassType, type))
+        return isinstance(obj, type)
 
     def raise_with_traceback(exc):
         exec('raise exc, None, sys.exc_info()[2]')
 
-    codepoint_to_chr = unichr
-    unicode_type = unicode
+    codepoint_to_chr = chr
+    unicode_type = str
 
 
 else:
@@ -70,10 +69,10 @@ def is_string(x):
         return isinstance(x, str)
 
     def iteritems(x):
-        return x.items()
+        return list(x.items())
 
     def itervalues(x):
-        return x.values()
+        return list(x.values())
 
     def is_class(obj):
         return isinstance(obj, type)
diff --git a/publish.py b/publish.py
index 79890ca..110dbdb 100755
--- a/publish.py
+++ b/publish.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 # vim:fileencoding=utf-8
 # License: BSD Copyright: 2017, Kovid Goyal <kovid at kovidgoyal.net>
 
diff --git a/run_tests.py b/run_tests.py
index 8e581cd..9385d84 100755
--- a/run_tests.py
+++ b/run_tests.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 
 """
 Note that the functional tests and doctests require test-tools to be on
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 0000000..2a9acf1
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,2 @@
+[bdist_wheel]
+universal = 1
diff --git a/setup.py b/setup.py
index f62cfc9..e076b0d 100755
--- a/setup.py
+++ b/setup.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 """Stateful programmatic web browsing.
 
 Stateful programmatic web browsing, after Andy Lester's Perl module
@@ -29,9 +29,6 @@
 if sys.version_info < (2, 7):
     raise SystemExit('mechanize requires python >= 2.7')
 
-if sys.version_info.major > 2:
-    raise SystemExit('mechanize only works on python 2.x')
-
 VERSION = open(os.path.join("mechanize", "_version.py")).\
     readlines()[0].strip(' "\n')
 
@@ -73,7 +70,7 @@ def main():
         version=VERSION,
         license="BSD",
         platforms=["any"],
-        install_requires=['html5lib>=0.999999999'],
+        install_requires=['html5lib>=0.999999999', 'six'],
         extras_require={'fast': ['html5-parser>=0.4.4']},
         classifiers=[c for c in CLASSIFIERS.split("\n") if c],
         zip_safe=True,
diff --git a/test-tools/testprogram.py b/test-tools/testprogram.py
index 707f392..4f58621 100644
--- a/test-tools/testprogram.py
+++ b/test-tools/testprogram.py
@@ -445,3 +445,6 @@ def parseArgs(self, argv):
 
 
 main = TestProgram
+
+if __name__ == '__main__':
+    main(sys.argv)
diff --git a/test/test_api.py b/test/test_api.py
index 877966c..d4c6393 100644
--- a/test/test_api.py
+++ b/test/test_api.py
@@ -6,7 +6,7 @@ class ImportTests(unittest.TestCase):
     def test_import_all(self):
         # the following will raise an exception if __all__ contains undefined
         # classes
-        from mechanize import *
+        import mechanize
 
 
 if __name__ == "__main__":
diff --git a/test/test_browser.doctest b/test/test_browser.doctest
index 57fd175..967695f 100644
--- a/test/test_browser.doctest
+++ b/test/test_browser.doctest
@@ -17,18 +17,18 @@ Opening a new response should close the old one.
 
 >>> br = TestHttpBrowser()
 >>> r = br.open("http://example.com")
->>> print response_impl(r)
+>>> print(response_impl(r))
 BytesIO
 >>> r2 = br.open("http://example.com")
->>> print response_impl(r2)
+>>> print(response_impl(r2))
 BytesIO
->>> print response_impl(r)
+>>> print(response_impl(r))
 eofresponse
 
 So should .set_response()
 
 >>> br.set_response(test_response())
->>> print response_impl(r2)
+>>> print(response_impl(r2))
 eofresponse
 
 
@@ -37,10 +37,10 @@ eofresponse
 >>> br = TestHttpBrowser()
 >>> r = br.open("http://example.com")
 >>> r2 = test_response(url="http://example.com/2")
->>> print response_impl(r2)
+>>> print(response_impl(r2))
 BytesIO
 >>> br.visit_response(r2)
->>> print response_impl(r)
+>>> print(response_impl(r))
 eofresponse
 >>> br.geturl() == br.request.get_full_url() == "http://example.com/2"
 True
@@ -174,7 +174,7 @@ True
 >>> test_state(br)
 True
 >>> req = Request("http://example.com")
->>> print req.visit
+>>> print(req.visit)
 None
 >>> r = br.open_novisit(req)
 >>> test_state(br)
diff --git a/test/test_browser.py b/test/test_browser.py
index f4affeb..90a687d 100644
--- a/test/test_browser.py
+++ b/test/test_browser.py
@@ -2,7 +2,7 @@
 """Tests for mechanize.Browser."""
 
 import copy
-import mimetools
+from email.message import Message
 import os
 import re
 from io import BytesIO
@@ -21,7 +21,7 @@
 
 # XXX these 'mock' classes are badly in need of simplification / removal
 # (note this stuff is also used by test_useragent.py and test_browser.doctest)
-class MockMethod:
+class MockMethod(object):
     def __init__(self, meth_name, action, handle):
         self.meth_name = meth_name
         self.handle = handle
@@ -36,6 +36,8 @@ def getheaders(self, name):
         name = name.lower()
         return [v for k, v in iteritems(self) if name == k.lower()]
 
+    get_all = getheaders
+
     def __delitem__(self, k):
         kmap = {q.lower(): q for q in self}
         k = kmap.get(k.lower())
@@ -43,11 +45,13 @@ def __delitem__(self, k):
             dict.__delitem__(self, k)
 
 
-class MockResponse:
+class MockResponse(object):
     closeable_response = None
 
     def __init__(self, url="http://example.com/", data=None, info=None):
         self.url = self._url = url
+        if not isinstance(data, bytes):
+            data = data.encode('utf-8')
         self.fp = BytesIO(data)
         if info is None:
             info = {}
@@ -212,8 +216,8 @@ def test_encoding(self):
             ("Content-Type: text/html; charset=UTF-8\r\n"
              "Content-Type: text/html; charset=KOI8-R\r\n\r\n", "UTF-8"),
         ]:
-            msg = mimetools.Message(BytesIO(s))
-            r = addinfourl(BytesIO(""), msg, "http://www.example.com/")
+            msg = Message(BytesIO(s.encode('utf-8')))
+            r = addinfourl(BytesIO(b""), msg, "http://www.example.com/")
             b.set_response(r)
             self.assertEqual(b.encoding(), ct)
 
@@ -786,15 +790,15 @@ def test_set_response(self):
         br.add_handler(make_mock_handler()([("http_open", r)]))
 
         r = br.open(url)
-        self.assertEqual(r.read(), html)
+        self.assertEqual(r.read(), html.encode('utf-8'))
         r.seek(0)
-        self.assertEqual(copy.copy(r).read(), html)
+        self.assertEqual(copy.copy(r).read(), html.encode('utf-8'))
         self.assertEqual(list(br.links())[0].url, "spam")
 
         newhtml = """<html><body><a href="eggs">click me</a></body></html>"""
 
         r.set_data(newhtml)
-        self.assertEqual(r.read(), newhtml)
+        self.assertEqual(r.read(), newhtml.encode('utf-8'))
         self.assertEqual(br.response().read(), html)
         br.response().set_data(newhtml)
         self.assertEqual(br.response().read(), html)
@@ -812,9 +816,9 @@ def test_select_form(self):
             <form name="a"></form>
             <form name="b" data-ac="123"></form>
             <form name="c" class="x"></form>
-            </html>''')
-        headers = mimetools.Message(
-            BytesIO("Content-type: text/html"))
+            </html>'''.encode('utf-8'))
+        headers = Message(
+            BytesIO("Content-type: text/html".encode('utf-8')))
         response = _response.response_seek_wrapper(
             _response.closeable_response(fp, headers, "http://example.com/",
                                          200, "OK"))
@@ -835,12 +839,13 @@ def test_str(self):
         br = TestBrowser()
         self.assertEqual(str(br), "<TestBrowser (not visiting a URL)>")
 
-        fp = BytesIO('<html><form name="f"><input /></form></html>')
-        headers = mimetools.Message(
-            BytesIO("Content-type: text/html"))
+        fp = BytesIO('<html><form name="f"><input /></form></html>'.encode('utf-8'))
+        headers = Message(
+            BytesIO("Content-type: text/html".encode('utf-8')))
         response = _response.response_seek_wrapper(
-            _response.closeable_response(fp, headers, "http://example.com/",
-                                         200, "OK"))
+            _response.closeable_response(
+                fp, headers, "http://example.com/",
+                200, "OK"))
         br.set_response(response)
         self.assertEqual(str(br), "<TestBrowser visiting http://example.com/>")
 
@@ -868,7 +873,7 @@ def do_nothing(*args, **kwds):
 
         def getresponse(self_):
             class Response(object):
-                msg = mimetools.Message(BytesIO(""))
+                msg = Message(BytesIO(b""))
                 status = 200
                 reason = "OK"
 
diff --git a/test/test_cookies.py b/test/test_cookies.py
index 181dd85..2dc588d 100644
--- a/test/test_cookies.py
+++ b/test/test_cookies.py
@@ -1,8 +1,10 @@
+from __future__ import unicode_literals
+
 """Tests for _clientcookie."""
 
 import errno
 import inspect
-import mimetools
+from email.message import Message
 import os
 import re
 import sys
@@ -24,8 +26,8 @@ def __init__(self, headers=[], url=None):
         """
         headers: list of RFC822-style 'Key: value' strings
         """
-        f = BytesIO("\n".join(headers))
-        self._headers = mimetools.Message(f)
+        f = BytesIO(b"\n".join(headers))
+        self._headers = Message(f)
         self._url = url
 
     def info(self):
diff --git a/test/test_functional.py b/test/test_functional.py
index 5d973b3..652c5a2 100644
--- a/test/test_functional.py
+++ b/test/test_functional.py
@@ -470,9 +470,9 @@ def test_new_response(self):
         self.assertEqual(br.response().get_data(), data)
 
     def hidden_test_close_pickle_load(self):
-        print ("Test test_close_pickle_load is expected to fail unless Python "
-               "standard library patch http://python.org/sf/1144636 has been "
-               "applied")
+        print("Test test_close_pickle_load is expected to fail unless Python "
+              "standard library patch http://python.org/sf/1144636 has been "
+              "applied")
         import pickle
 
         b = self.make_browser()
diff --git a/test/test_opener.doctest b/test/test_opener.doctest
index 39baa66..892fb24 100644
--- a/test/test_opener.doctest
+++ b/test/test_opener.doctest
@@ -4,11 +4,11 @@
 Normal case.  Response goes through hook function and is returned.
 
 >>> def urlopen(fullurl, data=None, timeout=None):
-...     print "fullurl %r" % fullurl
-...     print "data %r" % data
+...     print("fullurl %r" % fullurl)
+...     print("data %r" % data)
 ...     return "response"
 >>> def response_hook(response):
-...     print "response %r" % response
+...     print("response %r" % response)
 ...     return "processed response"
 >>> _opener.wrapped_open(urlopen, response_hook,
 ...                      "http://example.com", "data"
@@ -23,19 +23,19 @@ Raised HTTPError exceptions still go through the response hook but
 the result is raised rather than returned.
 
 >>> def urlopen(fullurl, data=None, timeout=None):
-...     print "fullurl %r" % fullurl
-...     print "data %r" % data
+...     print("fullurl %r" % fullurl)
+...     print("data %r" % data)
 ...     raise HTTPError(
 ...         "http://example.com", 200, "OK", {}, StringIO.StringIO())
 >>> def response_hook(response):
-...     print "response class", response.__class__.__name__
+...     print("response class", response.__class__.__name__)
 ...     return Exception("processed response")
 >>> try:
 ...     _opener.wrapped_open(urlopen, response_hook,
 ...                          "http://example.com", "data"
 ...                          )
 ... except Exception as exc:
-...     print exc
+...     print(exc)
 fullurl 'http://example.com'
 data 'data'
 response class HTTPError
@@ -44,15 +44,15 @@ processed response
 Other exceptions get ignored, since they're not response objects.
 
 >>> def urlopen(fullurl, data=None, timeout=None):
-...     print "fullurl %r" % fullurl
-...     print "data %r" % data
+...     print("fullurl %r" % fullurl)
+...     print("data %r" % data)
 ...     raise Exception("not caught")
 >>> try:
 ...     _opener.wrapped_open(urlopen, response_hook,
 ...                          "http://example.com", "data"
 ...                          )
 ... except Exception as exc:
-...     print exc
+...     print(exc)
 fullurl 'http://example.com'
 data 'data'
 not caught
diff --git a/test/test_request.doctest b/test/test_request.doctest
index ecaac29..86dc039 100644
--- a/test/test_request.doctest
+++ b/test/test_request.doctest
@@ -60,7 +60,7 @@ True
 [('Foo-Bar', 'baz'), ('Spam-Eggs', 'blah')]
 >>> r.has_header("Not-there")
 False
->>> print r.get_header("Not-there")
+>>> print(r.get_header("Not-there"))
 None
 >>> r.get_header("Not-there", "default")
 'default'
diff --git a/test/test_urllib2.py b/test/test_urllib2.py
index da9abcb..4644c67 100644
--- a/test/test_urllib2.py
+++ b/test/test_urllib2.py
@@ -136,7 +136,7 @@ def test_request_headers_methods():
 
     >>> r.has_header("Not-there")
     False
-    >>> print r.get_header("Not-there")
+    >>> print(r.get_header("Not-there"))
     None
     >>> r.get_header("Not-there", "default")
     'default'
@@ -291,7 +291,7 @@ def http_message(mapping):
     for kv in iteritems(mapping):
         f.append("%s: %s" % kv)
     f.append("")
-    msg = HTTPMessage(BytesIO("\r\n".join(f)))
+    msg = HTTPMessage(BytesIO("\r\n".join(f).encode('utf-8')))
     return msg
 
 
@@ -438,13 +438,13 @@ def reset(self):
         self.requests = []
 
     def http_open(self, req):
-        import mimetools
+        from email.message import Message
         import copy
         self.requests.append(copy.deepcopy(req))
         if self._count == 0:
             self._count = self._count + 1
             name = "Not important"
-            msg = mimetools.Message(BytesIO(self.headers))
+            msg = Message(BytesIO(self.headers.encode('utf-8')))
             return self.parent.error("http", req,
                                      test_response(), self.code, name, msg)
         else:
@@ -1236,12 +1236,12 @@ def __init__(self):
                 self.requests = []
 
             def http_open(self, req):
-                import mimetools
+                from email.message import Message
                 import copy
                 self.requests.append(copy.deepcopy(req))
                 if req.get_full_url() == "http://example.com/robots.txt":
                     hdr = "Location: http://example.com/en/robots.txt\r\n\r\n"
-                    msg = mimetools.Message(BytesIO(hdr))
+                    msg = Message(BytesIO(hdr))
                     return self.parent.error("http", req,
                                              test_response(), 302, "Blah", msg)
                 else:
diff --git a/test/test_urllib2_localnet.py b/test/test_urllib2_localnet.py
index 1dc0f22..4601099 100644
--- a/test/test_urllib2_localnet.py
+++ b/test/test_urllib2_localnet.py
@@ -2,7 +2,7 @@
 
 """Functional tests from the Python standard library test suite."""
 
-import mimetools
+from email.message import Message
 import threading
 import mechanize
 import unittest
@@ -492,9 +492,9 @@ def test_info(self):
 
         open_url = mechanize.urlopen("http://localhost:%s" % handler.port)
         info_obj = open_url.info()
-        self.assertTrue(isinstance(info_obj, mimetools.Message),
+        self.assertTrue(isinstance(info_obj, Message),
                         "object returned by 'info' is not an instance of "
-                        "mimetools.Message")
+                        "Message")
         self.assertEqual(info_obj.getsubtype(), "plain")
 
     def test_geturl(self):