Fix pylint unused-* warnings in webkitpy/tool.

third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/abstractlocalservercommand.py

 # Copyright (C) 2011 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:
 #
 # 1.  Redistributions of source code must retain the above copyright
 #     notice, this list of conditions and the following disclaimer.
 # 2.  Redistributions in binary form must reproduce the above copyright
 #     notice, this list of conditions and the following disclaimer in the
@@ skipping 23 matching lines @@
 
     def __init__(self):
         options = [
             make_option("--httpd-port", action="store", type="int", default=8127, help="Port to use for the HTTP server"),
             make_option("--no-show-results", action="store_false", default=True, dest="show_results",
                         help="Don't launch a browser with the rebaseline server"),
         ]
         super(AbstractLocalServerCommand, self).__init__(options=options)
 
     def _prepare_config(self, options, args, tool):
-        return None
+        raise NotImplementedError('Subclasses should implement this method.')

[qyearsley, 2016/06/02 16:41:32]

Currently, all subclasses implement this, so the behavior will be the same.

 
     def execute(self, options, args, tool):
         config = self._prepare_config(options, args, tool)
 
         server_url = "http://localhost:%d%s" % (options.httpd_port, self.launch_path)
         print "Starting server at %s" % server_url
         print "Use the 'Exit' link in the UI, %squitquitquit or Ctrl-C to stop" % server_url
 
         if options.show_results:
             # FIXME: This seems racy.
             threading.Timer(0.1, lambda: self._tool.user.open_url(server_url)).start()
 
         httpd = self.server(httpd_port=options.httpd_port, config=config)  # pylint: disable=E1102
         httpd.serve_forever()