执行python manage.py makemigrations时报错TypeError: __init__() missing 1 required positional argument: 'on_delete'

在执行python manage.py makemigrations时报错：

TypeError: __init__() missing 1 required positional argument: 'on_delete'

解决方法：

 

 

在连接外键时加上：

on_delete=models.CASCADE