'Return a deferred for the HTTP download'

def download_request(self, request, spider):

    agent = ScrapyAgent(contextFactory=self._contextFactory, pool=self._pool, maxsize=getattr(spider, 'download_maxsize', self._default_maxsize), warnsize=getattr(spider, 'download_warnsize', self._default_warnsize), fail_on_dataloss=self._fail_on_dataloss)
    return agent.download_request(request)
