Remove doctests module. It is now part of Python.

setuptools/command/test.py

@@ -20,7 +20,6 @@ class ScanningLoader(TestLoader):
         the return value to the tests.
         """
         tests = []
-        if module.__name__ != 'setuptools.tests.doctest':  # ugh
         tests.append(TestLoader.loadTestsFromModule(self, module))
 
         if hasattr(module, "additional_tests"):

setuptools/tests/__init__.py

@@ -2,7 +2,7 @@
 import sys
 import os
 import unittest
-from setuptools.tests import doctest
+import doctest
 import distutils.core
 import distutils.cmd
 from distutils.errors import DistutilsOptionError, DistutilsPlatformError
@@ -18,7 +18,6 @@ from setuptools import Feature
 from setuptools.depends import Require
 
 def additional_tests():
-    import doctest, unittest
     suite = unittest.TestSuite((
         doctest.DocFileSuite(
             os.path.join('tests', 'api_tests.txt'),