Provide a friendlier error message after Rietveld issue deletion.

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 495 matching lines @@
           ('\nFailed to diff against upstream branch %s!\n\n'
            'This branch probably doesn\'t exist anymore. To reset the\n'
            'tracking branch, please run\n'
            '    git branch --set-upstream %s trunk\n'
            'replacing trunk with origin/master or the relevant branch') %
           (upstream_branch, self.GetBranch()))
 
     issue = ConvertToInteger(self.GetIssue())
     patchset = ConvertToInteger(self.GetPatchset())
     if issue:
-      description = self.GetDescription()
+      try:
+        description = self.GetDescription()
+      except urllib2.HTTPError, e:

[M-A Ruel, 2012/01/04 17:56:51]

I'd prefer to have this at line 448 so all calls would be properly handled.

+        if e.code == 404:
+          DieWithError(
+              ('\nWhile fetching the description for issue %d, received a 404\n'
+               '(not found) error. It is likely that you deleted this issue\n'
+               'on the server. If this is the case, please run\n'
+               '    git cl issue 0\n'
+               'to clear the association with the deleted issue, and then run\n'
+               'this command again.') % issue)
+        else:
+          DieWithError('\nFailed to fetch description. HTTP error ' + e.code)
     else:
       # If the change was never uploaded, use the log messages of all commits
       # up to the branch point, as git cl upload will prefill the description
       # with these log messages.
       description = RunCommand(['git', 'log', '--pretty=format:%s%n%n%b',
                                 '%s...' % (upstream_branch)]).strip()
 
     if not author:
       author = RunGit(['config', 'user.email']).strip() or None
     return presubmit_support.GitChange(
@@ skipping 889 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:]))