Uses an existing method to delete pkg_resources

ez_setup.py

@@ -125,12 +125,7 @@ def _do_download(version, download_base, to_dir, download_delay):
     # Remove previously-imported pkg_resources if present (see
     # https://bitbucket.org/pypa/setuptools/pull-request/7/ for details).
     if 'pkg_resources' in sys.modules:
-        del_modules = [
-            name for name in sys.modules 
-            if name.startswith('pkg_resources')
-        ]
-        for mod_name in del_modules:
-            del sys.modules[mod_name]
+        _unload_pkg_resources()
 
     import setuptools
     setuptools.bootstrap_install_from = egg