Add comment to Distutil files about requiring 1.5.2 compatibility, as
    suggested by PEP 291.
diff --git a/Lib/distutils/file_util.py b/Lib/distutils/file_util.py
index c2fa086..e230ce5 100644
--- a/Lib/distutils/file_util.py
+++ b/Lib/distutils/file_util.py
@@ -3,6 +3,8 @@
 Utility functions for operating on single files.
 """
 
+# This module should be kept compatible with Python 1.5.2.
+
 __revision__ = "$Id$"
 
 import os