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

trychange.py

-#!/usr/bin/python
-# Copyright (c) 2009 The Chromium Authors. All rights reserved.
+#!/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.
 
 """Client-side script to send a try job to the try server. It communicates to
 the try server by either writting to a svn repository or by directly connecting
 to the server by HTTP.
 """
 
 import datetime
 import errno
 import getpass
 import logging
 import optparse
 import os
 import posixpath
 import re
 import shutil
 import sys
 import tempfile
 import urllib
 
 try:
   import simplejson as json  # pylint: disable=F0401
 except ImportError:
   try:
-    import json
+    import json  # pylint: disable=F0401
   except ImportError:
-    json = None
+    # Import the one included in depot_tools.
+    sys.path.append(os.path.join(os.path.dirname(__file__), 'third_party'))
+    import simplejson as json  # pylint: disable=F0401
 
-try:
-  import breakpad  # pylint: disable=W0611
-except ImportError:
-  pass
+import breakpad  # pylint: disable=W0611
 
-try:
-  import gcl
-except ImportError:
-  gcl = None
-
+import gcl
 import fix_encoding
 import gclient_utils
 import scm
 
 __version__ = '1.2'
 
 
 # Constants
 HELP_STRING = "Sorry, Tryserver is not available."
 USAGE = r"""%prog [options]
@@ skipping 713 matching lines @@
     return 1
   except gclient_utils.Error, e:
     print >> sys.stderr, e
     return 1
   return 0
 
 
 if __name__ == "__main__":
   fix_encoding.fix_encoding()
   sys.exit(TryChange(None, [], False))