关于Django Specifying a namespace in include() without providing an app_name

运行环境

PyCharm 2017.1
Django 2.0.1
python 3.6.1

在网页项目中使用include()方法

项目目录中同时存在app/urls.py和proj/urls.py
在proj/urls.py使用include方法

from django.urls import path,include
from app import urls as app_url
urlpatterns = [
    path('', include(app_url, namespace='common')),

在app/urls.py中对应url

from django.urls import path
from .views import index
urlpatterns = [
    path('',index,name='index'),
]

runserver发生错误

django.core.exceptions.ImproperlyConfigured:
Specifying a namespace in include() without providing an app_name is not supported.
Set the app_name attribute in the included module,
or pass a 2-tuple containing the list of patterns and app_name instead.

意思为：
在include方法里面指定namespace却不提供app_name是不允许的。
在包含的模块里设置app_name变量，或者在include方法里面提供app_name参数。

解决方法

方法1：在proj/urls.py中修改

from django.urls import path,include
from app import urls as app_url
urlpatterns = [
    path('', include((common_url,'common'), namespace='common')),
]

方法2：在app/urls.py中修改

from django.urls import path
from .views import index
app_name='common'
urlpatterns = [
    path('',index,name='index'),
]