with session_scope(self.Session) as session

[carrie0307]

您好，https://github.com/yidao620c/scrapy-cookbook/blob/master/source/scrapy-02.md 里代码中的with session_scope(self.Session) as session运行报错global name 'session_scope' is not defined;
查资料后有 from sqlalchemy.orm import scoped_session用scoped_session代替session_scope的，但是报错
AttributeError: exit
请问是我哪里搞错了吗？

新手学习，谢谢啦！