django2.0 include app_name

运行环境

PyCharm 2017.1
Django 2.0.1
python 3.6.1

错误代码如下：

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：在项目的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')),  #此处include后的第一个参数用元祖传两个值，第二个值为app_name
]

方法2：在app/urls.py中修改

from django.urls import path
from .views import index
app_name='common'  #此处增加app_name变量
urlpatterns = [
    path('',index,name='index'),
]