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

Tools/Scripts/webkitpy/common/checkout/scm/detection_unittest.py

 # Copyright (C) 2009 Google Inc. All rights reserved.
 # Copyright (C) 2009 Apple Inc. All rights reserved.
 # Copyright (C) 2011 Daniel Bates (dbates@intudata.com). All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #    * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
@@ skipping 10 matching lines @@
 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-import webkitpy.thirdparty.unittest2 as unittest
+import unittest
 
 from .detection import SCMDetector
 from webkitpy.common.system.filesystem_mock import MockFileSystem
 from webkitpy.common.system.executive_mock import MockExecutive
 from webkitpy.common.system.outputcapture import OutputCapture
 
 
 class SCMDetectorTest(unittest.TestCase):
     def test_detect_scm_system(self):
         filesystem = MockFileSystem()
         executive = MockExecutive(should_log=True)
         detector = SCMDetector(filesystem, executive)
 
         expected_logs = """\
 MOCK run_command: ['svn', 'info'], cwd=/
 MOCK run_command: ['git', 'rev-parse', '--is-inside-work-tree'], cwd=/
 """
         scm = OutputCapture().assert_outputs(self, detector.detect_scm_system, ["/"], expected_logs=expected_logs)
         self.assertIsNone(scm)
         # FIXME: This should make a synthetic tree and test SVN and Git detection in that tree.