copy_config <peer> <source> <target>
        eg. copy_config sw1 running startup

def do_copy_config(self, line):
        """copy_config <peer> <source> <target>
        eg. copy_config sw1 running startup
        """

        def f(p, args):
            try:
                source, target = args
            except:
                print("argument error")
                return
            print(p.copy_config(source, target))

        self._request(line, f)