Fix gerrit_util to use non None body.

gerrit_util.py

 # Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 Utilities for requesting information for a gerrit server via https.
 
 https://gerrit-review.googlesource.com/Documentation/rest-api.html
 """
 
@@ skipping 461 matching lines @@
     elif len(jmsg) > 1:
       raise GerritError(200, 'Multiple changes found for ChangeId %s.' % change)
     revision = jmsg[0]['current_revision']
   path = 'changes/%s/revisions/%s/review'
   return ReadHttpJsonResponse(CreateHttpConn(host, path))
 
 
 def AbandonChange(host, change, msg=''):
   """Abandon a gerrit change."""
   path = 'changes/%s/abandon' % change
-  body = {'message': msg} if msg else None
+  body = {'message': msg} if msg else {}
   conn = CreateHttpConn(host, path, reqtype='POST', body=body)
   return ReadHttpJsonResponse(conn, ignore_404=False)
 
 
 def RestoreChange(host, change, msg=''):
   """Restore a previously abandoned change."""
   path = 'changes/%s/restore' % change
-  body = {'message': msg} if msg else None
+  body = {'message': msg} if msg else {}
   conn = CreateHttpConn(host, path, reqtype='POST', body=body)
   return ReadHttpJsonResponse(conn, ignore_404=False)
 
 
 def SubmitChange(host, change, wait_for_merge=True):
   """Submits a gerrit change via Gerrit."""
   path = 'changes/%s/submit' % change
   body = {'wait_for_merge': wait_for_merge}
   conn = CreateHttpConn(host, path, reqtype='POST', body=body)
   return ReadHttpJsonResponse(conn, ignore_404=False)
@@ skipping 104 matching lines @@
         username = review.get('email', jmsg.get('name', ''))
         raise GerritError(200, 'Unable to set %s label for user "%s"'
                        ' on change %s.' % (label, username, change))
   jmsg = GetChangeCurrentRevision(host, change)
   if not jmsg:
     raise GerritError(
         200, 'Could not get review information for change "%s"' % change)
   elif jmsg[0]['current_revision'] != revision:
     raise GerritError(200, 'While resetting labels on change "%s", '
                    'a new patchset was uploaded.' % change)