Modeling after Astropy's technique for bundling libraries, the imports are now much cleaner. Thanks @embray. Ref #229.

27 files changed, 77 insertions, 160 deletions

diff --git a/pytest.ini b/pytest.ini
index 351942f4..bfb4e4f8 100755
--- a/pytest.ini
+++ b/pytest.ini
@@ -1,3 +1,3 @@
 [pytest]
 addopts=--doctest-modules --ignore release.py --ignore setuptools/lib2to3_ex.py --ignore tests/manual_test.py --ignore tests/shlib_test --doctest-glob=pkg_resources/api_tests.txt --ignore scripts/upload-old-releases-as-zip.py
-norecursedirs=dist build *.egg
+norecursedirs=dist build *.egg setuptools/extern
diff --git a/setuptools/__init__.py b/setuptools/__init__.py
index 6e1e5aa4..ec0d5dc2 100644
--- a/setuptools/__init__.py
+++ b/setuptools/__init__.py
@@ -8,12 +8,7 @@ from distutils.core import Command as _Command
 from distutils.util import convert_path
 from fnmatch import fnmatchcase
 
-try:
-    from setuptools._vendor.six.moves import filterfalse
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    from six.moves import filterfalse
+from setuptools.extern.six.moves import filterfalse
 
 import setuptools.version
 from setuptools.extension import Extension
diff --git a/setuptools/command/bdist_egg.py b/setuptools/command/bdist_egg.py
index 78164819..9cebd7fa 100644
--- a/setuptools/command/bdist_egg.py
+++ b/setuptools/command/bdist_egg.py
@@ -11,12 +11,7 @@ import os
 import marshal
 import textwrap
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 from pkg_resources import get_build_platform, Distribution, ensure_directory
 from pkg_resources import EntryPoint
diff --git a/setuptools/command/develop.py b/setuptools/command/develop.py
index c401c8d4..11b5df10 100755
--- a/setuptools/command/develop.py
+++ b/setuptools/command/develop.py
@@ -5,12 +5,7 @@ import os
 import glob
 import io
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 from pkg_resources import Distribution, PathMetadata, normalize_path
 from setuptools.command.easy_install import easy_install
diff --git a/setuptools/command/easy_install.py b/setuptools/command/easy_install.py
index 51c38ddf..a11618d1 100755
--- a/setuptools/command/easy_install.py
+++ b/setuptools/command/easy_install.py
@@ -40,14 +40,8 @@ import subprocess
 import shlex
 import io
 
-try:
-    from setuptools._vendor import six
-    from setuptools._vendor.six.moves import configparser
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
-    from six.moves import configparser
+from setuptools.extern import six
+from setuptools.extern.six.moves import configparser
 
 from setuptools import Command
 from setuptools.sandbox import run_setup
diff --git a/setuptools/command/egg_info.py b/setuptools/command/egg_info.py
index 5b996a11..cf46d24a 100755
--- a/setuptools/command/egg_info.py
+++ b/setuptools/command/egg_info.py
@@ -14,12 +14,7 @@ import io
 import warnings
 import time
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 from setuptools import Command
 from setuptools.command.sdist import sdist
diff --git a/setuptools/command/rotate.py b/setuptools/command/rotate.py
index 1ee1c538..804f962a 100755
--- a/setuptools/command/rotate.py
+++ b/setuptools/command/rotate.py
@@ -3,12 +3,7 @@ from distutils import log
 from distutils.errors import DistutilsOptionError
 import os
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 from setuptools import Command
 
diff --git a/setuptools/command/sdist.py b/setuptools/command/sdist.py
index 59990cd6..6640d4e3 100755
--- a/setuptools/command/sdist.py
+++ b/setuptools/command/sdist.py
@@ -5,12 +5,7 @@ import os
 import sys
 import io
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 from setuptools.utils import cs_path_exists
 
diff --git a/setuptools/command/setopt.py b/setuptools/command/setopt.py
index 1441e512..7f332be5 100755
--- a/setuptools/command/setopt.py
+++ b/setuptools/command/setopt.py
@@ -4,12 +4,7 @@ from distutils.errors import DistutilsOptionError
 import distutils
 import os
 
-try:
-    from setuptools._vendor.six.moves import configparser
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    from six.moves import configparser
+from setuptools.extern.six.moves import configparser
 
 from setuptools import Command
 
diff --git a/setuptools/command/test.py b/setuptools/command/test.py
index 32ff7f15..3a2a9b93 100644
--- a/setuptools/command/test.py
+++ b/setuptools/command/test.py
@@ -2,12 +2,7 @@ from distutils.errors import DistutilsOptionError
 from unittest import TestLoader
 import sys
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 from pkg_resources import (resource_listdir, resource_exists, normalize_path,
                            working_set, _namespace_packages,
diff --git a/setuptools/command/upload_docs.py b/setuptools/command/upload_docs.py
index 60e9fb7e..ca35a3ce 100644
--- a/setuptools/command/upload_docs.py
+++ b/setuptools/command/upload_docs.py
@@ -16,14 +16,8 @@ import tempfile
 import sys
 import shutil
 
-try:
-    from setuptools._vendor import six
-    from setuptools._vendor.six.moves import http_client, urllib
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
-    from six.moves import http_client, urllib
+from setuptools.extern import six
+from setuptools.extern.six.moves import http_client, urllib
 
 from pkg_resources import iter_entry_points
 
diff --git a/setuptools/depends.py b/setuptools/depends.py
index e633c05b..9f7c9a35 100644
--- a/setuptools/depends.py
+++ b/setuptools/depends.py
@@ -4,12 +4,7 @@ import marshal
 from imp import PKG_DIRECTORY, PY_COMPILED, PY_SOURCE, PY_FROZEN
 from distutils.version import StrictVersion
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 __all__ = [
     'Require', 'find_module', 'get_module_constant', 'extract_constant'
diff --git a/setuptools/dist.py b/setuptools/dist.py
index 11b42d19..70731225 100644
--- a/setuptools/dist.py
+++ b/setuptools/dist.py
@@ -13,12 +13,7 @@ from distutils.core import Distribution as _Distribution
 from distutils.errors import (DistutilsOptionError, DistutilsPlatformError,
     DistutilsSetupError)
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 from setuptools.depends import Require
 from setuptools import windows_support
diff --git a/setuptools/extern/__init__.py b/setuptools/extern/__init__.py
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/setuptools/extern/__init__.py
diff --git a/setuptools/extern/six.py b/setuptools/extern/six.py
new file mode 100644
index 00000000..2685c5e6
--- /dev/null
+++ b/setuptools/extern/six.py
@@ -0,0 +1,46 @@
+"""
+Handle loading six package from system or from the bundled copy
+"""
+
+import imp
+
+
+_SIX_SEARCH_PATH = ['setuptools._vendor.six', 'six']
+
+
+def _find_module(name, path=None):
+    """
+    Alternative to `imp.find_module` that can also search in subpackages.
+    """
+
+    parts = name.split('.')
+
+    for part in parts:
+        if path is not None:
+            path = [path]
+
+        fh, path, descr = imp.find_module(part, path)
+
+    return fh, path, descr
+
+
+def _import_six(search_path=_SIX_SEARCH_PATH):
+    for mod_name in search_path:
+        try:
+            mod_info = _find_module(mod_name)
+        except ImportError:
+            continue
+
+        imp.load_module(__name__, *mod_info)
+
+        break
+
+    else:
+        raise ImportError(
+            "The 'six' module of minimum version {0} is required; "
+            "normally this is bundled with this package so if you get "
+            "this warning, consult the packager of your "
+            "distribution.")
+
+
+_import_six()
diff --git a/setuptools/package_index.py b/setuptools/package_index.py
index 08c36890..ea136c09 100755
--- a/setuptools/package_index.py
+++ b/setuptools/package_index.py
@@ -14,14 +14,8 @@ try:
 except ImportError:
     from urllib2 import splituser
 
-try:
-    from setuptools._vendor import six
-    from setuptools._vendor.six.moves import urllib, http_client, configparser
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
-    from six.moves import urllib, http_client, configparser
+from setuptools.extern import six
+from setuptools.extern.six.moves import urllib, http_client, configparser
 
 from pkg_resources import (
     CHECKOUT_DIST, Distribution, BINARY_DIST, normalize_path, SOURCE_DIST,
diff --git a/setuptools/sandbox.py b/setuptools/sandbox.py
index 47d7f40c..37035f37 100755
--- a/setuptools/sandbox.py
+++ b/setuptools/sandbox.py
@@ -8,14 +8,8 @@ import re
 import contextlib
 import pickle
 
-try:
-    from setuptools._vendor import six
-    from setuptools._vendor.six.moves import builtins
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
-    from six.moves import builtins
+from setuptools.extern import six
+from setuptools.extern.six.moves import builtins
 
 import pkg_resources
 
diff --git a/setuptools/ssl_support.py b/setuptools/ssl_support.py
index 327c2fcb..7baedd19 100644
--- a/setuptools/ssl_support.py
+++ b/setuptools/ssl_support.py
@@ -3,12 +3,7 @@ import socket
 import atexit
 import re
 
-try:
-    from setuptools._vendor.six.moves import urllib, http_client
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    from six.moves import urllib, http_client
+from setuptools.extern.six.moves import urllib, http_client
 
 import pkg_resources
 from pkg_resources import ResolutionError, ExtractionError
diff --git a/setuptools/tests/__init__.py b/setuptools/tests/__init__.py
index 0a625993..32447356 100644
--- a/setuptools/tests/__init__.py
+++ b/setuptools/tests/__init__.py
@@ -8,12 +8,7 @@ from distutils.errors import DistutilsSetupError
 from distutils.core import Extension
 from distutils.version import LooseVersion
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 import pytest
 
 import setuptools.dist
diff --git a/setuptools/tests/contexts.py b/setuptools/tests/contexts.py
index 3a0ce6b5..8c9a2d3e 100644
--- a/setuptools/tests/contexts.py
+++ b/setuptools/tests/contexts.py
@@ -5,12 +5,7 @@ import sys
 import contextlib
 import site
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 
 @contextlib.contextmanager
diff --git a/setuptools/tests/server.py b/setuptools/tests/server.py
index ef5c8f62..6a687937 100644
--- a/setuptools/tests/server.py
+++ b/setuptools/tests/server.py
@@ -4,12 +4,7 @@
 import time
 import threading
 
-try:
-    from setuptools._vendor.six.moves import BaseHTTPServer, SimpleHTTPServer
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    from six.moves import BaseHTTPServer, SimpleHTTPServer
+from setuptools.extern.six.moves import BaseHTTPServer, SimpleHTTPServer
 
 
 class IndexServer(BaseHTTPServer.HTTPServer):
diff --git a/setuptools/tests/test_develop.py b/setuptools/tests/test_develop.py
index 71aaed6a..1b844499 100644
--- a/setuptools/tests/test_develop.py
+++ b/setuptools/tests/test_develop.py
@@ -5,12 +5,7 @@ import site
 import sys
 import io
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 import pytest
 
diff --git a/setuptools/tests/test_easy_install.py b/setuptools/tests/test_easy_install.py
index de34ca27..94e317b3 100644
--- a/setuptools/tests/test_easy_install.py
+++ b/setuptools/tests/test_easy_install.py
@@ -16,14 +16,8 @@ import itertools
 import distutils.errors
 import io
 
-try:
-    from setuptools._vendor import six
-    from setuptools._vendor.six.moves import urllib
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
-    from six.moves import urllib
+from setuptools.extern import six
+from setuptools.extern.six.moves import urllib
 
 import pytest
 try:
diff --git a/setuptools/tests/test_integration.py b/setuptools/tests/test_integration.py
index 1c574020..04772ba5 100644
--- a/setuptools/tests/test_integration.py
+++ b/setuptools/tests/test_integration.py
@@ -7,14 +7,7 @@ import glob
 import os
 import sys
 
-try:
-    from setuptools._vendor.six.moves import urllib
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    from six.moves import urllib
-
-
+from setuptools.extern.six.moves import urllib
 import pytest
 
 from setuptools.command.easy_install import easy_install
diff --git a/setuptools/tests/test_packageindex.py b/setuptools/tests/test_packageindex.py
index 649e8a4e..6a76b5fc 100644
--- a/setuptools/tests/test_packageindex.py
+++ b/setuptools/tests/test_packageindex.py
@@ -4,14 +4,8 @@ import sys
 import os
 import distutils.errors
 
-try:
-    from setuptools._vendor import six
-    from setuptools._vendor.six.moves import urllib, http_client
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
-    from six.moves import urllib, http_client
+from setuptools.extern import six
+from setuptools.extern.six.moves import urllib, http_client
 
 from .textwrap import DALS
 import pkg_resources
diff --git a/setuptools/tests/test_sdist.py b/setuptools/tests/test_sdist.py
index ea176733..753b507d 100644
--- a/setuptools/tests/test_sdist.py
+++ b/setuptools/tests/test_sdist.py
@@ -9,12 +9,7 @@ import unicodedata
 import contextlib
 import io
 
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 import pytest
 
diff --git a/setuptools/unicode_utils.py b/setuptools/unicode_utils.py
index 1fdb0a91..18903d9e 100644
--- a/setuptools/unicode_utils.py
+++ b/setuptools/unicode_utils.py
@@ -1,13 +1,7 @@
 import unicodedata
 import sys
 
-
-try:
-    from setuptools._vendor import six
-except ImportError:
-    # fallback to naturally-installed version; allows system packagers to
-    #  omit vendored packages.
-    import six
+from setuptools.extern import six
 
 # HFS Plus uses decomposed UTF-8
 def decompose(path):