Fix git-try, was broken by r58936.

git-try

 #!/usr/bin/python
 # Copyright (c) 2010 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.
 """Wrapper for trychange.py for git checkout."""
 
 import logging
 import sys
 
 import breakpad
 
+import gclient_utils
 from scm import GIT
 import trychange
 
 
 def GetRietveldIssueNumber():
-  return GIT.Capture(
-      ['config', 'branch.%s.rietveldissue' % GIT.GetBranch(None)],
-      error_ok=True)[0]
+  try:
+    return GIT.Capture(
+        ['config', 'branch.%s.rietveldissue' % GIT.GetBranch(None)])
+  except gclient_utils.Error:
+    return None
 
 
 def GetRietveldPatchsetNumber():
-  return GIT.Capture(
-      ['config', 'branch.%s.rietveldpatchset' % GIT.GetBranch(None)],
-      error_ok=True)[0]
+  try:
+    return GIT.Capture(
+        ['config', 'branch.%s.rietveldpatchset' % GIT.GetBranch(None)])
+  except gclient_utils.Error:
+    return None
 
 
 def GetRietveldServerUrl():
-  return GIT.Capture(
-      ['config', 'rietveld.server'], error_ok=True)[0].strip()
+  try:
+    return GIT.Capture(['config', 'rietveld.server']).strip()
+  except gclient_utils.Error:
+    return None
 
 
 if __name__ == '__main__':
   args = sys.argv[:]
   patchset = GetRietveldPatchsetNumber()
   if patchset:
     args.extend([
         '--issue', GetRietveldIssueNumber(),
         '--patchset', patchset,
     ])
   else:
     rietveld_url = GetRietveldServerUrl()
     if rietveld_url:
       args.extend(['--rietveld_url', GetRietveldServerUrl()])
   # Hack around a limitation in logging.
   logging.getLogger().handlers = []
   sys.exit(trychange.TryChange(
     args, file_list=[], swallow_exception=False,
     prog='git-try',
     extra_epilog='\n'
                   'git-try will diff against your tracked branch and will '
                       'detect your rietveld\n'
                   'code review if you are using git-cl\n'))