Deferred中的scrapy未处理错误：

报错关键字builtins.TypeError:'NoneType'objectisnotiterablestart_requests=iter(self.spider.start_requests())builtins.TypeError:'NoneType'objectisnotiterable报错代码Deferred:Traceback中未处理的错误（最近调用最后）:文件“c:\users\17293\appdata\local\programs\python\python37\lib\site-packages\scrapy\crawler.py”，第192行，在crawlreturnself._crawl(crawler,*args,**kwargs)文件“c:\users\17293\appdata\local\programs\python\python37\lib\site-packages\scrapy\crawler.py”，第196行，在_crawld=crawler.crawl(*args,**kwargs)文件“c:\users\17293\appdata\local\programs\python\python37\lib\site-packages\twisted\internet\defer.py”，第1613行，在unwindGenerator中返回_cancellableInlineCallbacks(gen)文件“c:\users\17293\appdata\local\programs\python\python37\lib\site-packages\twisted\internet\defer.py"，第1529行，在_cancellableInlineCallbacks_inlineCallbacks(None,g,status)------文件“c:\users\17293\appdata\local\programs\python\python37\lib\site-packages\twisted\internet\defer.py”，第1418行，在_inlineCallbacksresult=g.send(result)File“c:\users\17293\appdata\local\programs\python\python37\lib\site-packages\scrapy\crawler.py",line88,incrawlstart_requests=iter(self.spider.start_requests())builtins.TypeError:'NoneType'objectisnotiterable原因scrapycrawlspier_name-sLOG_FILE=all.log