Validates a namespace, raising a ResponseFailed error if invalid.

        Args:
            state_root (str): The state_root to validate

        Raises:
            ResponseFailed: The state_root was invalid, and a status of
                INVALID_ROOT will be sent with the response.

def _validate_namespace(self, namespace):
        """Validates a namespace, raising a ResponseFailed error if invalid.

        Args:
            state_root (str): The state_root to validate

        Raises:
            ResponseFailed: The state_root was invalid, and a status of
                INVALID_ROOT will be sent with the response.
        """
        if self._namespace_regex.fullmatch(namespace) is None:
            LOGGER.debug('Invalid namespace: %s', namespace)
            raise _ResponseFailed(self._status.INVALID_ADDRESS)