Remove remaining unused imports in webkitpy.

third_party/WebKit/Tools/Scripts/webkitpy/common/checkout/scm/scm.py

 # Copyright (c) 2009, Google Inc. All rights reserved.
 # Copyright (c) 2009 Apple 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
@@ skipping 16 matching lines @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 # Python module for interacting with an SCM system (like SVN or Git)
 
 import logging
 import re
 import sys
 
 from webkitpy.common.system.executive import Executive
-from webkitpy.common.system.executive import ScriptError
 from webkitpy.common.system.filesystem import FileSystem
 
 _log = logging.getLogger(__name__)
 
 
 # SCM methods are expected to return paths relative to self.checkout_root.
 class SCM:
 
     # Arguments are generally unused in abstract base methods below.
     # pylint: disable=unused-argument
@@ skipping 103 matching lines @@
     #--------------------------------------------------------------------------
     # Subclasses must indicate if they support local commits,
     # but the SCM baseclass will only call local_commits methods when this is true.
     @staticmethod
     def supports_local_commits():
         SCM._subclass_must_implement()
 
     def commit_locally_with_message(self, message):
         _log.error("Your source control manager does not support local commits.")
         sys.exit(1)