备忘： django admin界面报模板错误， 说是下面这一行有问题： {% url django-admindocs-docroot as docsroot %}. 排查发现是url.py里配置有问题导致的，错误信息很不明显。
(The error is showing up where it is because the admin uses {% url django- admindocs-docroot as docsroot %} to conditionally include a Documentation link on each admin page, based on whether the admindocs urls have been configured. This template tag will result in all of your url patterns being evaluated, and problems with any will be reported. You need to find the app you are running that has a registration/views.py file that imports oldforms and upgrade it to use current forms.)