Use distutils.debug.DEBUG instead of distutils.core.DEBUG.

Note that distutils.core.DEBUG still works if client code uses it, but
the core code avoids circular references by using distutils.debug.

Lib/distutils/core.py

@@ -13,10 +13,7 @@ __revision__ = "$Id$"
 import sys, os
 from types import *
 
-# If DISTUTILS_DEBUG is anything other than the empty string, we run in
-# debug mode.
-DEBUG = os.environ.get('DISTUTILS_DEBUG')
-
+from distutils.debug import DEBUG
 from distutils.errors import *
 from distutils.util import grok_environment_error
 
@@ -25,7 +22,6 @@ from distutils.dist import Distribution
 from distutils.cmd import Command
 from distutils.extension import Extension
 
-
 # This is a barebones help message generated displayed when the user
 # runs the setup script with no arguments at all.  More useful help
 # is generated with various --help options: global help, list commands,