Update an existing endpoint
        :param endpoint: is the updated endpoint the client wants to update

def update_endpoint(self, endpoint):
        """
        Update an existing endpoint
        :param endpoint: is the updated endpoint the client wants to update
        """
        self._validate_uuid(endpoint.endpoint_id)
        self._validate_subscriber_id(endpoint.subscriber_id)

        url = "/notification/v1/endpoint/{}".format(endpoint.endpoint_id)
        response = NWS_DAO().putURL(
            url, self._write_headers(), self._json_body(endpoint.json_data()))

        if response.status != 204:
            raise DataFailureException(url, response.status, response.data)
        return response.status