Disable purging of distutils/setuptools during sandbox operations. Ref #315.

CHANGES.txt

@@ -8,10 +8,6 @@ CHANGES
 
 * Issue #314: Disabled support for ``setup_requires`` metadata to avoid issue
   where Setuptools was unable to upgrade over earlier versions.
-* Issue #315: Updated setuptools to hide its own loaded modules during
-  installation of another package. This change will enable setuptools to
-  upgrade (or downgrade) itself even when its own metadata and implementation
-  change.
 
 ---
 8.4

setuptools/sandbox.py

@@ -126,7 +126,9 @@ def setup_context(setup_dir):
     temp_dir = os.path.join(setup_dir, 'temp')
     with save_pkg_resources_state():
         with save_modules():
-            hide_setuptools()
+            # Disabled per
+            # https://bitbucket.org/pypa/setuptools/issue/315/setuptools-should-always-use-its-own#comment-14512075
+            # hide_setuptools()
             with save_path():
                 with save_argv():
                     with override_temp(temp_dir):