django.core.exceptions.ImproperlyConfigured: The included URLconf 's9luffycity.urls' does not appear to have any patterns in it. If you see valid patterns in the file then the issue is probably caused

出现问题：

$ python manage.py runserver

启动项目报错时候

raise ImproperlyConfigured(msg.format(name=self.urlconf_name))
django.core.exceptions.ImproperlyConfigured: The included URLconf 's9luffycity.urls' does not appear to have any patterns in it. If you see valid patterns in the file then the issue is
probably caused by a circular import.

原因：

settings中的s9luffycity.url循环调用？？？

解决办法：

重新安装django

$ pip install django==2.2