Add an alert for python < 2.5.

gcl.py

 #!/usr/bin/python
 # Copyright (c) 2010 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.
 
 """\
 Wrapper script around Rietveld's upload.py that simplifies working with groups
 of files.
 """
 
@@ skipping 1333 matching lines @@
   print sys.modules[__name__].__doc__
   print 'version ' + __version__ + '\n'
 
   print('Commands are:\n' + '\n'.join([
         '  %-12s %s' % (fn[3:], Command(fn[3:]).__doc__.split('\n')[0].strip())
         for fn in dir(sys.modules[__name__]) if fn.startswith('CMD')]))
   return 0
 
 
 def main(argv):
+  if sys.hexversion < 0x02050000:
+    print >> sys.stderr, (
+        '\nYour python version is unsupported, please upgrade.\n')
   if not argv:
     argv = ['help']
   command = Command(argv[0])
   # Help can be run from anywhere.
   if command == CMDhelp:
     return command(argv[1:])
 
   try:
     GetRepositoryRoot()
   except gclient_utils.Error:
@@ skipping 25 matching lines @@
     if e.code != 500:
       raise
     print >> sys.stderr, (
         'AppEngine is misbehaving and returned HTTP %d, again. Keep faith '
         'and retry or visit go/isgaeup.\n%s') % (e.code, str(e))
     return 1
 
 
 if __name__ == "__main__":
   sys.exit(main(sys.argv[1:]))