Run pychecker over most scripts in depot_tools. Catched a few bugs.

tests/trychange_unittest.py

 #!/usr/bin/python
 # Copyright (c) 2009 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 trychange.py."""
 
 import optparse
 import unittest
 
@@ skipping 11 matching lines @@
 
 
 class TryChangeUnittest(TryChangeTestsBase):
   """General trychange.py tests."""
   def testMembersChanged(self):
     members = [
       'EscapeDot', 'GIT', 'GetSourceRoot',
       'GetTryServerSettings', 'GuessVCS',
       'HELP_STRING', 'InvalidScript', 'NoTryServerAccess', 'PathDifference',
       'RunCommand', 'SCM', 'SVN', 'TryChange', 'USAGE',
-      'datetime', 'gcl', 'gclient', 'gclient_scm', 'getpass', 'logging',
+      'datetime', 'gcl', 'gclient_scm', 'getpass', 'logging',
       'optparse', 'os', 'presubmit_support', 'shutil', 'socket', 'subprocess',
-      'sys', 'tempfile', 'traceback', 'upload', 'urllib',
+      'sys', 'tempfile', 'upload', 'urllib',
     ]
     # If this test fails, you should add the relevant test.
     self.compareMembers(trychange, members)
 
 
 class SVNUnittest(TryChangeTestsBase):
   """trychange.SVN tests."""
   def setUp(self):
     self.fake_root = '/fake_root'
     self.expected_files = ['foo.txt', 'bar.txt']
@@ skipping 47 matching lines @@
   def testGetLocalRoot(self):
     self.mox.StubOutWithMock(upload, 'RunShell')
     upload.RunShell(['git', 'rev-parse', '--show-cdup']).AndReturn(
         self.fake_root)
     self.mox.ReplayAll()
     self.assertEqual(self.git.GetLocalRoot(), self.fake_root)
 
 
 if __name__ == '__main__':
   unittest.main()