django2.0 报错 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.

raise ImproperlyConfigured(msg.format(name=self.urlconf_name))
django.core.exceptions.ImproperlyConfigured: 
The included URLconf '<module 'users.urls' from 'D:\mygitfile\meiduo_project\meiduo_mall\meiduo_mall\apps\users\urls.py'>' 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.

错误来源：配置子应用的url时，启动django项目报错

错误原因：启动django项目，django框架会加载路由配置，如果在总路由添加了子应用，

那么需要在子应用文件下新建一个urls.py文件 并且要加上 urlpatterns=[]

例如：主应用 url.py

"""meiduo_mall URL Configuration

The `urlpatterns` list routes URLs to views. For more information please see:
    https://docs.djangoproject.com/en/2.0/topics/http/urls/
Examples:
Function views
    1. Add an import:  from my_app import views
    2. Add a URL to urlpatterns:  path('', views.home, name='home')
Class-based views
    1. Add an import:  from other_app.views import Home
    2. Add a URL to urlpatterns:  path('', Home.as_view(), name='home')
Including another URLconf
    1. Import the include() function: from django.urls import include, path
    2. Add a URL to urlpatterns:  path('blog/', include('blog.urls'))
"""
from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path('admin/', admin.site.urls),
    path('users/', include(('users.urls', 'users'), namespace='users')),
]

子应用urls.py

from django.urls import path
from . import views

urlpatterns=[
    path('register/',views.RegisterView.as_view(),name='register')
]