Use underscores to separate words in filenames in webkitpy.

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

 # Copyright 2016 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.
 
 import logging
 import unittest
 
-from webkitpy.common.system.logtesting import LoggingTestCase, LogTesting, TestLogStream
+from webkitpy.common.system.log_testing import LoggingTestCase, LogTesting, TestLogStream
 
 
 class TestLogStreamTest(unittest.TestCase):
 
     def test_passed_to_stream_handler(self):
         stream = TestLogStream(self)
         handler = logging.StreamHandler(stream)
         logger = logging.getLogger('test.logger')
         logger.addHandler(handler)
         logger.setLevel(logging.INFO)
@@ skipping 32 matching lines @@
             'INFO: Informative message\n',
             'WARNING: Warning message\n',
         ])
 
     @staticmethod
     def example_logging_code():
         logger = logging.getLogger('test.logger')
         logger.debug('Debugging message')
         logger.info('Informative message')
         logger.warning('Warning message')