Introduce a new monkey module to encapsulate the monkeypatching.

setuptools/__init__.py

@@ -5,7 +5,6 @@ import sys
 import functools
 import distutils.core
 import distutils.filelist
-from distutils.core import Command as _Command
 from distutils.util import convert_path
 from fnmatch import fnmatchcase
 
@@ -13,7 +12,8 @@ from setuptools.extern.six.moves import filterfalse, map
 
 import setuptools.version
 from setuptools.extension import Extension
-from setuptools.dist import Distribution, Feature, _get_unpatched
+from setuptools.dist import Distribution, Feature
+from setuptools.monkey import _get_unpatched
 from setuptools.depends import Require
 
 __all__ = [
@@ -122,7 +122,7 @@ find_packages = PackageFinder.find
 
 setup = distutils.core.setup
 
-_Command = _get_unpatched(_Command)
+_Command = _get_unpatched(distutils.core.Command)
 
 
 class Command(_Command):

setuptools/dist.py

@@ -9,7 +9,6 @@ import distutils.log
 import distutils.core
 import distutils.cmd
 import distutils.dist
-from distutils.core import Distribution as _Distribution
 from distutils.errors import (DistutilsOptionError, DistutilsPlatformError,
     DistutilsSetupError)
 from distutils.util import rfc822_escape
@@ -20,25 +19,11 @@ from pkg_resources.extern import packaging
 
 from setuptools.depends import Require
 from setuptools import windows_support
+from setuptools.monkey import _get_unpatched
 import pkg_resources
 
 
-def _get_unpatched(cls):
-    """Protect against re-patching the distutils if reloaded
-
-    Also ensures that no other distutils extension monkeypatched the distutils
-    first.
-    """
-    while cls.__module__.startswith('setuptools'):
-        cls, = cls.__bases__
-    if not cls.__module__.startswith('distutils'):
-        raise AssertionError(
-            "distutils has already been patched by %r" % cls
-        )
-    return cls
-
-
-_Distribution = _get_unpatched(_Distribution)
+_Distribution = _get_unpatched(distutils.core.Distribution)
 
 
 def _patch_distribution_metadata_write_pkg_file():

setuptools/extension.py

@@ -7,7 +7,7 @@ import distutils.extension
 
 from setuptools.extern.six.moves import map
 
-from .dist import _get_unpatched
+from .monkey import _get_unpatched
 from . import msvc
 
 _Extension = _get_unpatched(distutils.core.Extension)

setuptools/monkey.py

+"""
+Monkey patching of distutils.
+"""
+
+
+__all__ = []
+"everything is private"
+
+
+def _get_unpatched(cls):
+    """Protect against re-patching the distutils if reloaded
+
+    Also ensures that no other distutils extension monkeypatched the distutils
+    first.
+    """
+    while cls.__module__.startswith('setuptools'):
+        cls, = cls.__bases__
+    if not cls.__module__.startswith('distutils'):
+        raise AssertionError(
+            "distutils has already been patched by %r" % cls
+        )
+    return cls