diff --git a/src/rez/bind/_utils.py b/src/rez/bind/_utils.py
index fe315dd4d..aefe6484c 100644
--- a/src/rez/bind/_utils.py
+++ b/src/rez/bind/_utils.py
@@ -8,6 +8,7 @@
 from rez.util import which
 from rez.utils.system import popen
 from rez.utils.logging_ import print_debug
+from rez.vendor.six import six
 from pipes import quote
 import subprocess
 import os.path
@@ -16,6 +17,9 @@
 import sys
 
 
+basestring = six.string_types[0]
+
+
 def log(msg):
     if config.debug("bind_modules"):
         print_debug(msg)
diff --git a/src/rez/cli/forward.py b/src/rez/cli/forward.py
index 18bd93885..ac6c515eb 100644
--- a/src/rez/cli/forward.py
+++ b/src/rez/cli/forward.py
@@ -1,9 +1,13 @@
 """See util.create_forwarding_script()."""
 import argparse
+from rez.vendor.six import six
 
 __doc__ = argparse.SUPPRESS
 
 
+basestring = six.string_types[0]
+
+
 def setup_parser(parser, completions=False):
     parser.add_argument("YAML", type=str)
     parser.add_argument("ARG", type=str, nargs=argparse.REMAINDER)
diff --git a/src/rez/config.py b/src/rez/config.py
index 1ae029b44..894408139 100644
--- a/src/rez/config.py
+++ b/src/rez/config.py
@@ -21,6 +21,9 @@
 import copy
 
 
+basestring = six.string_types[0]
+
+
 # -----------------------------------------------------------------------------
 # Schema Implementations
 # -----------------------------------------------------------------------------
diff --git a/src/rez/developer_package.py b/src/rez/developer_package.py
index 53242ca47..a14145a86 100644
--- a/src/rez/developer_package.py
+++ b/src/rez/developer_package.py
@@ -7,11 +7,15 @@
 from rez.utils.sourcecode import SourceCode
 from rez.utils.logging_ import print_info, print_error
 from rez.vendor.enum import Enum
+from rez.vendor.six import six
 from inspect import isfunction
 import os.path
 import stat
 
 
+basestring = six.string_types[0]
+
+
 class PreprocessMode(Enum):
     """Defines when a package preprocess will be executed.
     """
diff --git a/src/rez/package_copy.py b/src/rez/package_copy.py
index 78c71bcbc..e020c3af2 100644
--- a/src/rez/package_copy.py
+++ b/src/rez/package_copy.py
@@ -13,6 +13,10 @@
 from rez.utils.logging_ import print_info, print_warning
 from rez.utils.filesystem import replacing_symlink, replacing_copy, \
     safe_makedirs, additive_copytree, make_path_writable, get_existing_path
+from rez.vendor.six import six
+
+
+basestring = six.string_types[0]
 
 
 def copy_package(package, dest_repository, variants=None, shallow=False,
diff --git a/src/rez/package_filter.py b/src/rez/package_filter.py
index b2a790079..a97d74f55 100644
--- a/src/rez/package_filter.py
+++ b/src/rez/package_filter.py
@@ -2,12 +2,16 @@
 from rez.exceptions import ConfigurationError
 from rez.config import config
 from rez.utils.data_utils import cached_property, cached_class_property
+from rez.vendor.six import six
 from rez.vendor.version.requirement import VersionedObject, Requirement
 from hashlib import sha1
 import fnmatch
 import re
 
 
+basestring = six.string_types[0]
+
+
 class PackageFilterBase(object):
     def excludes(self, package):
         """Determine if the filter excludes the given package.
diff --git a/src/rez/package_help.py b/src/rez/package_help.py
index 50c0186be..5ff01b2b8 100644
--- a/src/rez/package_help.py
+++ b/src/rez/package_help.py
@@ -6,6 +6,7 @@
 from rez.utils.system import popen
 from rez.utils.backcompat import convert_old_command_expansions
 from rez.utils.scope import scoped_formatter
+from rez.vendor.six import six
 from rez.system import system
 import subprocess
 import webbrowser
@@ -13,6 +14,9 @@
 import sys
 
 
+basestring = six.string_types[0]
+
+
 class PackageHelp(object):
     """Object for extracting and viewing help for a package.
 
diff --git a/src/rez/package_maker__.py b/src/rez/package_maker__.py
index dd80dd402..13288e421 100644
--- a/src/rez/package_maker__.py
+++ b/src/rez/package_maker__.py
@@ -11,11 +11,15 @@
 from rez.packages_ import Package
 from rez.package_py_utils import expand_requirement
 from rez.vendor.schema.schema import Schema, Optional, Or, Use, And
+from rez.vendor.six import six
 from rez.vendor.version.version import Version
 from contextlib import contextmanager
 import os
 
 
+basestring = six.string_types[0]
+
+
 # this schema will automatically harden request strings like 'python-*'; see
 # the 'expand_requires' function for more info.
 #
diff --git a/src/rez/package_py_utils.py b/src/rez/package_py_utils.py
index 207591cd4..8ef487613 100644
--- a/src/rez/package_py_utils.py
+++ b/src/rez/package_py_utils.py
@@ -9,6 +9,10 @@
 # these imports just forward the symbols into this module's namespace
 from rez.utils.system import popen
 from rez.exceptions import InvalidPackageError
+from rez.vendor.six import six
+
+
+basestring = six.string_types[0]
 
 
 def expand_requirement(request, paths=None):
diff --git a/src/rez/package_resources_.py b/src/rez/package_resources_.py
index 97451d5da..61e32a59a 100644
--- a/src/rez/package_resources_.py
+++ b/src/rez/package_resources_.py
@@ -17,6 +17,9 @@
 from hashlib import sha1
 
 
+basestring = six.string_types[0]
+
+
 # package attributes created at release time
 package_release_keys = (
     "timestamp",
diff --git a/src/rez/package_serialise.py b/src/rez/package_serialise.py
index ce8ffdfe6..f350cb117 100644
--- a/src/rez/package_serialise.py
+++ b/src/rez/package_serialise.py
@@ -11,6 +11,10 @@
 from rez.utils.schema import Required
 from rez.utils.yaml import dump_yaml
 from pprint import pformat
+from rez.vendor.six import six
+
+
+basestring = six.string_types[0]
 
 
 # preferred order of keys in a package definition file
diff --git a/src/rez/package_test.py b/src/rez/package_test.py
index a19e59c8a..e2c5b6a6a 100644
--- a/src/rez/package_test.py
+++ b/src/rez/package_test.py
@@ -3,12 +3,16 @@
 from rez.packages_ import get_latest_package_from_string, Variant
 from rez.exceptions import PackageNotFoundError, PackageTestError
 from rez.utils.colorize import heading, Printer
+from rez.vendor.six import six
 from pipes import quote
 import subprocess
 import time
 import sys
 
 
+basestring = six.string_types[0]
+
+
 class PackageTestRunner(object):
     """Object for running a package's tests.
 
diff --git a/src/rez/packages_.py b/src/rez/packages_.py
index 0e14d7a2e..2e17d5022 100644
--- a/src/rez/packages_.py
+++ b/src/rez/packages_.py
@@ -12,11 +12,14 @@
 from rez.exceptions import PackageFamilyNotFoundError, ResourceError
 from rez.vendor.version.version import VersionRange
 from rez.vendor.version.requirement import VersionedObject
+from rez.vendor.six import six
 from rez.serialise import FileFormat
 from rez.config import config
 import sys
 
 
+basestring = six.string_types[0]
+
 # ------------------------------------------------------------------------------
 # package-related classes
 # ------------------------------------------------------------------------------
diff --git a/src/rez/plugin_managers.py b/src/rez/plugin_managers.py
index 4860f1743..56891688f 100644
--- a/src/rez/plugin_managers.py
+++ b/src/rez/plugin_managers.py
@@ -6,11 +6,15 @@
 from rez.utils.schema import dict_to_schema
 from rez.utils.data_utils import LazySingleton, cached_property, deep_update
 from rez.utils.logging_ import print_debug, print_warning
+from rez.vendor.six import six
 from rez.exceptions import RezPluginError
 import os.path
 import sys
 
 
+basestring = six.string_types[0]
+
+
 # modified from pkgutil standard library:
 # this function is called from the __init__.py files of each plugin type inside
 # the 'rezplugins' package.
diff --git a/src/rez/resolved_context.py b/src/rez/resolved_context.py
index f3d9a4434..4456f5e2f 100644
--- a/src/rez/resolved_context.py
+++ b/src/rez/resolved_context.py
@@ -23,6 +23,7 @@
 from rez.shells import create_shell
 from rez.exceptions import ResolvedContextError, PackageCommandError, RezError
 from rez.utils.graph_utils import write_dot, write_compacted, read_graph_from_string
+from rez.vendor.six import six
 from rez.vendor.version.version import VersionRange
 from rez.vendor.enum import Enum
 from rez.vendor import yaml
@@ -42,6 +43,9 @@
 import os.path
 
 
+basestring = six.string_types[0]
+
+
 class RezToolsVisibility(Enum):
     """Determines if/how rez cli tools are added back to PATH within a
     resolved environment."""
diff --git a/src/rez/rex.py b/src/rez/rex.py
index 95f41bf20..db7e9a5e1 100644
--- a/src/rez/rex.py
+++ b/src/rez/rex.py
@@ -18,6 +18,10 @@
 from rez.utils.data_utils import AttrDictWrapper
 from rez.utils.formatting import expandvars
 from rez.vendor.enum import Enum
+from rez.vendor.six import six
+
+
+basestring = six.string_types[0]
 
 
 #===============================================================================
diff --git a/src/rez/shells.py b/src/rez/shells.py
index df696d7c3..9bae5992a 100644
--- a/src/rez/shells.py
+++ b/src/rez/shells.py
@@ -10,12 +10,16 @@
 from rez.exceptions import RezSystemError
 from rez.rex import EscapedString
 from rez.config import config
+from rez.vendor.six import six
 import subprocess
 import os
 import os.path
 import pipes
 
 
+basestring = six.string_types[0]
+
+
 def get_shell_types():
     """Returns the available shell types: bash, tcsh etc."""
     from rez.plugin_managers import plugin_manager
diff --git a/src/rez/suite.py b/src/rez/suite.py
index 9e84e9e20..6c65d9b00 100644
--- a/src/rez/suite.py
+++ b/src/rez/suite.py
@@ -9,6 +9,7 @@
 from rez.vendor import yaml
 from rez.vendor.yaml.error import YAMLError
 from rez.utils.yaml import dump_yaml
+from rez.vendor.six import six
 from collections import defaultdict
 import os
 import os.path
@@ -16,6 +17,9 @@
 import sys
 
 
+basestring = six.string_types[0]
+
+
 class Suite(object):
     """A collection of contexts.
 
diff --git a/src/rez/tests/test_resources_.py b/src/rez/tests/test_resources_.py
index 97fda4978..c016f2a38 100644
--- a/src/rez/tests/test_resources_.py
+++ b/src/rez/tests/test_resources_.py
@@ -9,6 +9,10 @@
 from rez.exceptions import ResourceError
 import unittest
 from rez.vendor.schema.schema import Schema, Use, And, Optional
+from rez.vendor.six import six
+
+
+basestring = six.string_types[0]
 
 
 class PetResourceError(Exception):
diff --git a/src/rez/tests/test_shells.py b/src/rez/tests/test_shells.py
index 1e4a9dd6a..1b2c394d7 100644
--- a/src/rez/tests/test_shells.py
+++ b/src/rez/tests/test_shells.py
@@ -13,6 +13,7 @@
 from rez.util import which
 from rez.bind import hello_world
 from rez.utils.platform_ import platform_
+from rez.vendor.six import six
 import subprocess
 import tempfile
 import inspect
diff --git a/src/rez/utils/data_utils.py b/src/rez/utils/data_utils.py
index f57d1e741..92b2e1be8 100644
--- a/src/rez/utils/data_utils.py
+++ b/src/rez/utils/data_utils.py
@@ -5,6 +5,10 @@
 from rez.exceptions import RexError
 from collections import MutableMapping
 from threading import Lock
+from rez.vendor.six import six
+
+
+basestring = six.string_types[0]
 
 
 class ModifyList(object):
diff --git a/src/rez/utils/filesystem.py b/src/rez/utils/filesystem.py
index 338b609be..b7a386dd4 100644
--- a/src/rez/utils/filesystem.py
+++ b/src/rez/utils/filesystem.py
@@ -18,6 +18,8 @@
 import stat
 import platform
 
+from rez.vendor.six import six
+
 
 class TempDirs(object):
     """Tempdir manager.
@@ -477,10 +479,10 @@ def encode_filesystem_name(input_str):
     As an example, the string "Foo_Bar (fun).txt" would get encoded as:
         _foo___bar_020_028fun_029.txt
     """
-    if isinstance(input_str, str):
+    if isinstance(input_str, six.string_types):
         input_str = unicode(input_str)
     elif not isinstance(input_str, unicode):
-        raise TypeError("input_str must be a basestring")
+        raise TypeError("input_str must be a %s" % six.string_types[0].__name__)
 
     as_is = u'abcdefghijklmnopqrstuvwxyz0123456789.-'
     uppercase = u'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
diff --git a/src/rez/utils/graph_utils.py b/src/rez/utils/graph_utils.py
index eed17c2ea..416a2d93c 100644
--- a/src/rez/utils/graph_utils.py
+++ b/src/rez/utils/graph_utils.py
@@ -17,6 +17,10 @@
 from rez.vendor.pygraph.readwrite.dot import read as read_dot
 from rez.vendor.pygraph.algorithms.accessibility import accessibility
 from rez.vendor.pygraph.classes.digraph import digraph
+from rez.vendor.six import six
+
+
+basestring = six.string_types[0]
 
 
 def read_graph_from_string(txt):
diff --git a/src/rez/utils/memcached.py b/src/rez/utils/memcached.py
index f1b86ba59..79e3f87ba 100644
--- a/src/rez/utils/memcached.py
+++ b/src/rez/utils/memcached.py
@@ -8,6 +8,9 @@
 from inspect import getargspec, isgeneratorfunction
 from hashlib import md5
 from uuid import uuid4
+from rez.vendor.six import six
+
+basestring = six.string_types[0]
 
 
 # this version should be changed if and when the caching interface changes
diff --git a/src/rez/utils/schema.py b/src/rez/utils/schema.py
index be694203a..b6af6c3e7 100644
--- a/src/rez/utils/schema.py
+++ b/src/rez/utils/schema.py
@@ -1,9 +1,13 @@
 """
 Utilities for working with dict-based schemas.
 """
+from rez.vendor.six import six
 from rez.vendor.schema.schema import Schema, Optional, Use, And
 
 
+basestring = six.string_types[0]
+
+
 # an alias which just so happens to be the same number of characters as
 # 'Optional' so that our schema are easier to read
 Required = Schema
diff --git a/src/rezgui/widgets/ContextSettingsWidget.py b/src/rezgui/widgets/ContextSettingsWidget.py
index 935f14d14..adca7837c 100644
--- a/src/rezgui/widgets/ContextSettingsWidget.py
+++ b/src/rezgui/widgets/ContextSettingsWidget.py
@@ -4,11 +4,15 @@
 from rezgui.models.ContextModel import ContextModel
 from rez.config import config
 from rez.vendor import yaml
+from rez.vendor.six import six
 from rez.vendor.yaml.error import YAMLError
 from rez.vendor.schema.schema import Schema, SchemaError, Or, And, Use
 from functools import partial
 
 
+basestring = six.string_types[0]
+
+
 class ContextSettingsWidget(QtGui.QWidget, ContextViewMixin):
 
     titles = {
diff --git a/src/rezplugins/build_system/cmake.py b/src/rezplugins/build_system/cmake.py
index 57080898c..fe8dd8978 100644
--- a/src/rezplugins/build_system/cmake.py
+++ b/src/rezplugins/build_system/cmake.py
@@ -13,6 +13,7 @@
 from rez.config import config
 from rez.backport.shutilwhich import which
 from rez.vendor.schema.schema import Or
+from rez.vendor.six import six
 from rez.shells import create_shell
 import functools
 import os.path
@@ -20,6 +21,9 @@
 import os
 
 
+basestring = six.string_types[0]
+
+
 class RezCMakeError(BuildSystemError):
     pass
 
diff --git a/src/rezplugins/build_system/custom.py b/src/rezplugins/build_system/custom.py
index 83207e07c..c3ca1d21c 100644
--- a/src/rezplugins/build_system/custom.py
+++ b/src/rezplugins/build_system/custom.py
@@ -14,9 +14,13 @@
 from rez.exceptions import PackageMetadataError
 from rez.utils.colorize import heading, Printer
 from rez.utils.logging_ import print_warning
+from rez.vendor.six import six
 from rez.config import config
 
 
+basestring = six.string_types[0]
+
+
 class CustomBuildSystem(BuildSystem):
     """This build system runs the 'build_command' defined in a package.py.
 
diff --git a/src/rezplugins/package_repository/filesystem.py b/src/rezplugins/package_repository/filesystem.py
index f68461176..6b1a3b92b 100644
--- a/src/rezplugins/package_repository/filesystem.py
+++ b/src/rezplugins/package_repository/filesystem.py
@@ -27,9 +27,13 @@
 from rez.config import config
 from rez.backport.lru_cache import lru_cache
 from rez.vendor.schema.schema import Schema, Optional, And, Use, Or
+from rez.vendor.six import six
 from rez.vendor.version.version import Version, VersionRange
 
 
+basestring = six.string_types[0]
+
+
 debug_print = config.debug_printer("resources")
 
 
diff --git a/src/rezplugins/release_hook/amqp.py b/src/rezplugins/release_hook/amqp.py
index e6116b761..1baaa5813 100644
--- a/src/rezplugins/release_hook/amqp.py
+++ b/src/rezplugins/release_hook/amqp.py
@@ -6,9 +6,13 @@
 from rez.release_hook import ReleaseHook
 from rez.utils.logging_ import print_error, print_debug
 from rez.utils.amqp import publish_message
+from rez.vendor.six import six
 from rez.config import config
 
 
+basestring = six.string_types[0]
+
+
 class AmqpReleaseHook(ReleaseHook):
     """
     Publishes a message to the broker.
diff --git a/src/rezplugins/release_hook/command.py b/src/rezplugins/release_hook/command.py
index f73b72a6a..59644af01 100644
--- a/src/rezplugins/release_hook/command.py
+++ b/src/rezplugins/release_hook/command.py
@@ -16,9 +16,13 @@
 from rez.utils.scope import scoped_formatter
 from rez.utils.formatting import expandvars
 from rez.vendor.schema.schema import Schema, Or, Optional, Use, And
+from rez.vendor.six import six
 from rez.util import which
 
 
+basestring = six.string_types[0]
+
+
 class CommandReleaseHook(ReleaseHook):
 
     commands_schema = Schema(
diff --git a/src/rezplugins/release_hook/emailer.py b/src/rezplugins/release_hook/emailer.py
index 94c0fc975..7e5a4237d 100644
--- a/src/rezplugins/release_hook/emailer.py
+++ b/src/rezplugins/release_hook/emailer.py
@@ -10,11 +10,15 @@
 from rez.utils.yaml import load_yaml
 from rez.utils.scope import scoped_formatter
 from rez.vendor.schema.schema import Or
+from rez.vendor.six import six
 import os.path
 import smtplib
 import sys
 
 
+basestring = six.string_types[0]
+
+
 class EmailReleaseHook(ReleaseHook):
 
     schema_dict = {
diff --git a/src/rezplugins/shell/cmd.py b/src/rezplugins/shell/cmd.py
index 4a9d07d43..4134db046 100644
--- a/src/rezplugins/shell/cmd.py
+++ b/src/rezplugins/shell/cmd.py
@@ -8,12 +8,16 @@
 from rez.utils.system import popen
 from rez.utils.platform_ import platform_
 from rez.util import shlex_join
+from rez.vendor.six import six
 from functools import partial
 import os
 import re
 import subprocess
 
 
+basestring = six.string_types[0]
+
+
 class CMD(Shell):
     # For reference, the ss64 web page provides useful documentation on builtin
     # commands for the Windows Command Prompt (cmd).  It can be found here :