'Check the given response against the requirements defined by this
instance.
@param response: The response to check.
@type response: L{twisted.web.iweb.IResponse}
@return: A L{Deferred} that fires with C{None} after the response has
been found to satisfy all the requirements or that fires with a
L{Failure} if any part of the response is incorrect.'

def verify(self, response):

    reading = readBody(response)
    reading.addCallback(self.decode)
    reading.addCallback(self._verifyWithBody, response)
    return reading
