Fix all "dangerous-default-value" pylint warnings.

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

 # Copyright (c) 2016 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 103 matching lines @@
         if self.long_help:
             help_text += "%s\n\n" % self.long_help
         help_text += self.option_parser.format_option_help(optparse.IndentedHelpFormatter())
         return help_text
 
     def execute(self, options, args, tool):
         raise NotImplementedError("subclasses must implement")
 
     # main() exists so that Commands can be turned into stand-alone scripts.
     # Other parts of the code will likely require modification to work stand-alone.
-    def main(self, args=sys.argv):
-        (options, args) = self.parse_args(args)
+    def main(self, args=None):
+        options, args = self.parse_args(args)
         # Some commands might require a dummy tool
         return self.check_arguments_and_execute(options, args)
 
 
 class HelpPrintingOptionParser(optparse.OptionParser):
 
     def __init__(self, epilog_method=None, *args, **kwargs):
         self.epilog_method = epilog_method
         optparse.OptionParser.__init__(self, *args, **kwargs)
 
     def error(self, msg):
         self.print_usage(sys.stderr)
         error_message = "%s: error: %s\n" % (self.get_prog_name(), msg)
         # This method is overridden to add this one line to the output:
         error_message += "\nType \"%s --help\" to see usage.\n" % self.get_prog_name()
         self.exit(1, error_message)
 
     # We override format_epilog to avoid the default formatting which would paragraph-wrap the epilog
     # and also to allow us to compute the epilog lazily instead of in the constructor (allowing it to be context sensitive).
     def format_epilog(self, epilog):  # pylint: disable=unused-argument
         if self.epilog_method:
             return "\n%s\n" % self.epilog_method()
         return ""