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

git_cl.py

Index: git_cl.py
diff --git a/git_cl.py b/git_cl.py
index e7569e2669b8ccda1d65f560f07d301c5093c780..06b2692dd90257f3dcf28751d2b89bf398db9bb1 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -1,7 +1,12 @@
-#!/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
@@ -23,7 +28,7 @@ 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'))