Make certain no previous imports of old versions of pkg_resources are floating...

Make certain no previous imports of old versions of pkg_resources are floating around before importing the newly installed setuptools.

ez_setup.py

@@ -100,6 +100,8 @@ def _do_download(version, download_base, to_dir, download_delay):
                                       to_dir, download_delay)
         _build_egg(egg, tarball, to_dir)
     sys.path.insert(0, egg)
+    if 'pkg_resources' in sys.modules:
+        del sys.modules['pkg_resources']
     import setuptools
     setuptools.bootstrap_install_from = egg