tools/net/ynl: Add --output-json arg to ynl cli

from lib import YnlFamily, Netlink

class YnlEncoder(json.JSONEncoder):

    def default(self, obj):

        if isinstance(obj, bytes):

            return bytes.hex(obj)

        if isinstance(obj, set):

            return list(obj)

        return json.JSONEncoder.default(self, obj)

def main():

    parser = argparse.ArgumentParser(description='YNL CLI sample')

    parser.add_argument('--spec', dest='spec', type=str, required=True)

    parser.add_argument('--append', dest='flags', action='append_const',

                        const=Netlink.NLM_F_APPEND)

    parser.add_argument('--process-unknown', action=argparse.BooleanOptionalAction)

    parser.add_argument('--output-json', action='store_true')

    args = parser.parse_args()

    def output(msg):

        if args.output_json:

            print(json.dumps(msg, cls=YnlEncoder))

        else:

            pprint.PrettyPrinter().pprint(msg)

    if args.no_schema:

        args.schema = ''

    if args.do:

        reply = ynl.do(args.do, attrs, args.flags)

        pprint.PrettyPrinter().pprint(reply)

        output(reply)

    if args.dump:

        reply = ynl.dump(args.dump, attrs)

        pprint.PrettyPrinter().pprint(reply)

        output(reply)

    if args.ntf:

        ynl.check_ntf()

        pprint.PrettyPrinter().pprint(ynl.async_msg_queue)

        output(ynl.async_msg_queue)

if __name__ == "__main__":