No module named 'widgets'
https://blog.csdn.net/sunfellow2009/article/details/81452810
原因就是：django2.0 把原来的 django.core.urlresolvers 包 更改为了 django.urls包
https://www.cnblogs.com/liqu/p/9417729.html
url(r'^users/', include(('users.urls', 'users'), namespace='users')),
https://www.cnblogs.com/wendaobiancheng/p/9109257.html
No module named 'django.core.context_processors'
https://blog.csdn.net/com_ma/article/details/78742921