Added message when upstream branch is gone.

tests/git_cl_test.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.
 
 """Unit tests for git_cl.py."""
 
 import os
 import StringIO
 import stat
@@ skipping 68 matching lines @@
     self.calls = []
     self._calls_done = 0
     self.mock(subprocess2, 'call', self._mocked_call)
     self.mock(subprocess2, 'check_call', self._mocked_call)
     self.mock(subprocess2, 'check_output', self._mocked_call)
     self.mock(subprocess2, 'communicate', self._mocked_call)
     self.mock(git_common, 'is_dirty_git_tree', lambda x: False)
     self.mock(git_common, 'get_or_create_merge_base',
               lambda *a: (
                   self._mocked_call(['get_or_create_merge_base']+list(a))))
+    self.mock(git_cl, 'BranchExists', lambda _: True)
     self.mock(git_cl, 'FindCodereviewSettingsFile', lambda: '')
     self.mock(git_cl, 'ask_for_data', self._mocked_call)
     self.mock(git_cl.breakpad, 'post', self._mocked_call)
     self.mock(git_cl.breakpad, 'SendStack', self._mocked_call)
     self.mock(git_cl.presubmit_support, 'DoPresubmitChecks', PresubmitMock)
     self.mock(git_cl.rietveld, 'Rietveld', RietveldMock)
     self.mock(git_cl.rietveld, 'CachingRietveld', RietveldMock)
     self.mock(git_cl.upload, 'RealMain', self.fail)
     self.mock(git_cl.watchlists, 'Watchlists', WatchlistsMock)
     self.mock(git_cl.auth, 'get_authenticator_for_host', AuthenticatorMock)
@@ skipping 807 matching lines @@
     self.calls += [
       ((['git', 'apply', '--index', '-p0', '--3way'],), '',
        subprocess2.CalledProcessError(1, '', '', '', '')),
     ]
     self.assertNotEqual(git_cl.main(['patch', '123456']), 0)
 
 if __name__ == '__main__':
   git_cl.logging.basicConfig(
       level=git_cl.logging.DEBUG if '-v' in sys.argv else git_cl.logging.ERROR)
   unittest.main()