Remove thirdparty/unittest2 from webkitpy and require python2.7.

Tools/Scripts/webkitpy/common/system/systemhost_mock.py

 # Copyright (c) 2011 Google Inc. All rights reserved.
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 #     * Redistributions of source code must retain the above copyright
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 #     * Redistributions in binary form must reproduce the above
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 # in the documentation and/or other materials provided with the
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 # this software without specific prior written permission.
 #
 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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+
 from StringIO import StringIO
 
 from webkitpy.common.system.environment import Environment
 from webkitpy.common.system.executive_mock import MockExecutive
 from webkitpy.common.system.filesystem_mock import MockFileSystem
 from webkitpy.common.system.platforminfo_mock import MockPlatformInfo
 from webkitpy.common.system.user_mock import MockUser
 from webkitpy.common.system.workspace_mock import MockWorkspace
 
 
@@ skipping 19 matching lines @@
         return Environment({"MOCK_ENVIRON_COPY": '1'})
 
     def print_(self, *args, **kwargs):
         sep = kwargs.get('sep', ' ')
         end = kwargs.get('end', '\n')
         file = kwargs.get('file', None)
         stderr = kwargs.get('stderr', False)
 
         file = file or (self.stderr if stderr else self.stdout)
         file.write(sep.join([str(arg) for arg in args]) + end)