def format(self, status, headers, environ, bucket, delay):
        """
        Formats a response entity.  Returns a tuple of the desired
        status code and the formatted entity.  The default status code
        is passed in, as is a dictionary of headers.

        :param status: The default status code.  Should be returned to
                       the caller, or an alternate selected.  The
                       status code should include both the number and
                       the message, separated by a single space.
        :param headers: A dictionary of headers for the response.
                        Should update the 'Content-Type' header at a
                        minimum.
        :param environ: The WSGI environment for the request.
        :param bucket: The bucket containing the data which caused the
                       delay decision to be made.  This can be used to
                       obtain such information as the next time the
                       request can be made.
        :param delay: The number of seconds by which the request
                      should be delayed.
        """

        # This is a default response entity, which can be overridden
        # by limit subclasses.
        entity = ("This request was rate-limited.  "
                  "Please retry your request after %s." %
                  time.strftime("%Y-%m-%dT%H:%M:%SZ",
                                time.gmtime(bucket.next)))
        headers['Content-Type'] = 'text/plain'

        return status, entity
Formats a response entity.  Returns a tuple of the desired
        status code and the formatted entity.  The default status code
        is passed in, as is a dictionary of headers.

        :param status: The default status code.  Should be returned to
                       the caller, or an alternate selected.  The
                       status code should include both the number and
                       the message, separated by a single space.
        :param headers: A dictionary of headers for the response.
                        Should update the 'Content-Type' header at a
                        minimum.
        :param environ: The WSGI environment for the request.
        :param bucket: The bucket containing the data which caused the
                       delay decision to be made.  This can be used to
                       obtain such information as the next time the
                       request can be made.
        :param delay: The number of seconds by which the request
                      should be delayed.