Mock stdout to avoid pollutting test runner stdout.

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 1489 matching lines @@
     out = StringIO.StringIO()
     self.mock(git_cl.sys, 'stdout', out)
 
     self.mock(git_cl, 'Changelist', ChangelistMock)
     self.mock(git_cl.sys, 'stdin', StringIO.StringIO('hi \r\n\t there\n\nman'))
 
     self.assertEqual(0, git_cl.main(['description', '-n', '-']))
     self.assertEqual('hi\n\t there\n\nman', ChangelistMock.desc)
 
   def test_archive(self):
+    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
+
     self.calls = \
         [((['git', 'for-each-ref', '--format=%(refname)', 'refs/heads'],),
           'refs/heads/master\nrefs/heads/foo\nrefs/heads/bar'),
          ((['git', 'config', 'branch.master.rietveldissue'],), '1'),
          ((['git', 'config', 'rietveld.autoupdate'],), ''),
          ((['git', 'config', 'rietveld.server'],), ''),
          ((['git', 'config', 'rietveld.server'],), ''),
          ((['git', 'config', 'branch.foo.rietveldissue'],), '456'),
          ((['git', 'config', 'rietveld.server'],), ''),
          ((['git', 'config', 'rietveld.server'],), ''),
@@ skipping 14 matching lines @@
 
     self.mock(git_cl, 'get_cl_statuses',
               lambda branches, fine_grained, max_processes:
               [(MockChangelist('master', 1), 'open'),
                (MockChangelist('foo', 456), 'closed'),
                (MockChangelist('bar', 789), 'open')])
 
     self.assertEqual(0, git_cl.main(['archive', '-f']))
 
   def test_archive_current_branch_fails(self):
+    self.mock(git_cl.sys, 'stdout', StringIO.StringIO())
     self.calls = \
         [((['git', 'for-each-ref', '--format=%(refname)', 'refs/heads'],),
           'refs/heads/master'),
          ((['git', 'config', 'branch.master.rietveldissue'],), '1'),
          ((['git', 'config', 'rietveld.autoupdate'],), ''),
          ((['git', 'config', 'rietveld.server'],), ''),
          ((['git', 'config', 'rietveld.server'],), ''),
          ((['git', 'symbolic-ref', 'HEAD'],), 'master')]
 
     class MockChangelist():
@@ skipping 71 matching lines @@
         ((['rm_file_or_tree', '/abs/git_repo_root/.git/hooks/commit-msg'],),
          ''),
     ]
     cl._codereview_impl._GerritCommitMsgHookCheck(offer_removal=True)
 
 
 if __name__ == '__main__':
   git_cl.logging.basicConfig(
       level=git_cl.logging.DEBUG if '-v' in sys.argv else git_cl.logging.ERROR)
   unittest.main()