git_cl.py: emit a more helpful message when [git try] should be used instead of [git cl try].

git_cl.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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."""
 
 from distutils.version import LooseVersion
@@ skipping 2114 matching lines @@
         'Instead send your job to the parent.\n'
         'Bot list: %s' % builders_and_tests)
     return 1
 
   patchset = cl.GetMostRecentPatchset()
   if patchset and patchset != cl.GetPatchset():
     print(
         '\nWARNING Mismatch between local config and server. Did a previous '
         'upload fail?\ngit-cl try always uses latest patchset from rietveld. '
         'Continuing using\npatchset %s.\n' % patchset)
-
-  cl.RpcServer().trigger_try_jobs(
-      cl.GetIssue(), patchset, options.name, options.clobber, options.revision,
-      builders_and_tests)
+  try:
+    cl.RpcServer().trigger_try_jobs(
+        cl.GetIssue(), patchset, options.name, options.clobber,
+        options.revision, builders_and_tests)
+  except urllib2.HTTPError, e:
+    if e.code == 404:
+      print('404 from rietveld; '
+            'did you mean to use "git try" instead of "git cl try"?')
+      return 1
   print('Tried jobs on:')
   length = max(len(builder) for builder in builders_and_tests)
   for builder in sorted(builders_and_tests):
     print '  %*s: %s' % (length, builder, ','.join(builders_and_tests[builder]))
   return 0
 
 
 @subcommand.usage('[new upstream branch]')
 def CMDupstream(parser, args):
   """Prints or sets the name of the upstream branch, if any."""
@@ skipping 219 matching lines @@
         ('AppEngine is misbehaving and returned HTTP %d, again. Keep faith '
           'and retry or visit go/isgaeup.\n%s') % (e.code, str(e)))
 
 
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   colorama.init()
   sys.exit(main(sys.argv[1:]))