检查用户登录状态
    :param func: 需要被检查的函数

def check_login(func):
    """检查用户登录状态
    :param func: 需要被检查的函数
    """

    @wraps(func)
    def wrapper(*args, **kwargs):
        ret = func(*args, **kwargs)
        if type(ret) == requests.Response:
            # 检测结果是否为JSON
            if ret.content[0]!=b'{' and ret.content[0]!=b'[':
                return ret
            try:
                foo = json.loads(ret.content.decode('utf-8'))
                if 'errno' in foo and foo['errno'] == -6:
                    logging.debug(
                            'Offline, deleting cookies file then relogin.')
                    path = '.{0}.cookies'.format(args[0].username)
                    if os.path.exists(path):
                        os.remove(path)
                    args[0]._initiate()
            except:
                raise LoginFailed('User unsigned in.')
        return ret

    return wrapper