def fetch_command(self, subcommand):
        try:
            app_name = get_commands()[subcommand]
        except KeyError:
            sys.stderr.write("Unknown command: %r\nType '%s help' for usage.\n" % \
                (subcommand, self.prog_name))
            sys.exit(1)
        if isinstance(app_name, BaseCommand):
            # If the command is already loaded, use it directly.
            klass = app_name
        else:
            klass = load_command_class(app_name, subcommand)
        return klass
Tries to fetch the given subcommand, printing a message with the
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.2/django/core/management/__init__.py/ManagementUtility.fetch_command