在执行 scrapy crawl domz时，警告：
:0: UserWarning: You do not have a working installation of the service_identity module: 'cannot import name 'opentype''. Please install it from <https://pypi.python.org/pypi/service_identity> and make sure all of its dependencies are satisfied. Without the service_identity module, Twisted can perform only rudimentary TLS client hostname verification. Many valid certificate/hostname mappings may be rejected.:0: UserWarning: Y
