Remove remaining unused imports in webkitpy.

third_party/WebKit/Tools/Scripts/webkitpy/common/system/outputcapture.py

 # Copyright (c) 2009, Google Inc. 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.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 12 matching lines @@
 # 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.
 #
 # Class for unittest support.  Used for capturing stderr/stdout.
 
 import logging
 import sys
-import unittest
 
 from StringIO import StringIO
 
 
 class OutputCapture(object):
 
     def __init__(self):
         self.saved_outputs = dict()
         self._log_level = logging.INFO
 
@@ skipping 50 matching lines @@
             testassert = testcase.assertMultiLineEqual
         else:
             testassert = testcase.assertEqual
 
         testassert(stdout_string, expected_stdout)
         testassert(stderr_string, expected_stderr)
         if expected_logs is not None:
             testassert(logs_string, expected_logs)
         # This is a little strange, but I don't know where else to return this information.
         return return_value