Add a warning if the current version of python is not 2.5

git_cl.py

-#!/usr/bin/python
-# git-cl -- a git-command for integrating reviews on Rietveld
+#!/usr/bin/env python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
+"""A git-command for integrating reviews on Rietveld."""
+
 import errno
 import logging
 import optparse
 import os
 import re
 import subprocess
 import sys
 import tempfile
 import textwrap
 import urlparse
 import urllib2
 
 try:
   import readline  # pylint: disable=W0611
 except ImportError:
   pass
 
 try:
   import simplejson as json  # pylint: disable=F0401
 except ImportError:
   try:
-    import json
+    import json  # pylint: disable=F0401
   except ImportError:
     # Fall back to the packaged version.
     sys.path.append(os.path.join(os.path.dirname(__file__), 'third_party'))
     import simplejson as json
 
 
 from third_party import upload
 import breakpad  # pylint: disable=W0611
 import fix_encoding
 import presubmit_support
@@ skipping 1380 matching lines @@
              'and retry or visit go/isgaeup.\n%s') % (e.code, str(e)))
 
   # Not a known command. Default to help.
   GenUsage(parser, 'help')
   return CMDhelp(parser, argv)
 
 
 if __name__ == '__main__':
   fix_encoding.fix_encoding()
   sys.exit(main(sys.argv[1:]))