Do not throw an exception if git cl rebase fails.

git_cl.py

 #!/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 logging
@@ skipping 1284 matching lines @@
     print "Patch applied to index."
   return 0
 
 
 def CMDrebase(parser, args):
   """rebase current branch on top of svn repo"""
   # Provide a wrapper for git svn rebase to help avoid accidental
   # git svn dcommit.
   # It's the only command that doesn't use parser at all since we just defer
   # execution to git-svn.
-  subprocess2.check_call(['git', 'svn', 'rebase'] + args)
-  return 0
+  return subprocess2.call(['git', 'svn', 'rebase'] + args)
 
 
 def GetTreeStatus():
   """Fetches the tree status and returns either 'open', 'closed',
   'unknown' or 'unset'."""
   url = settings.GetTreeStatusUrl(error_ok=True)
   if url:
     status = urllib2.urlopen(url).read().lower()
     if status.find('closed') != -1 or status == '0':
       return 'closed'
@@ skipping 115 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:]))