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 428 matching lines @@
     self.GetIssue()
     return self.rietveld_server
 
   def GetIssueURL(self):
     """Get the URL for a particular issue."""
     return '%s/%s' % (self.GetRietveldServer(), self.GetIssue())
 
   def GetDescription(self, pretty=False):
     if not self.has_description:
       if self.GetIssue():
-        self.description = self.RpcServer().get_description(
-            int(self.GetIssue())).strip()
+        issue = int(self.GetIssue())
+        try:
+          self.description = self.RpcServer().get_description(issue).strip()
+        except urllib2.HTTPError, e:
+          if e.code == 404:
+            DieWithError(
+                ('\nWhile fetching the description for issue %d, received a '
+                 '404 (not found)\n'
+                 'error. It is likely that you deleted this '
+                 'issue on the server. If this is the\n'
+                 'case, please run\n\n'
+                 '    git cl issue 0\n\n'
+                 'to clear the association with the deleted issue. Then run '
+                 'this command again.') % issue)
+          else:
+            DieWithError(
+                '\nFailed to fetch issue description. HTTP error ' + e.code)
       self.has_description = True
     if pretty:
       wrapper = textwrap.TextWrapper()
       wrapper.initial_indent = wrapper.subsequent_indent = '  '
       return wrapper.fill(self.description)
     return self.description
 
   def GetPatchset(self):
     if not self.has_patchset:
       patchset = RunGit(['config', self._PatchsetSetting()],
@@ skipping 955 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:]))