RuntimeError: You called this URL via POST, but the URL doesn't end in a slash and you have APPEND_SLASH set. Django can't redirect to the slash URL while maintaining POST data. Change your form to point to 127.0.0.1:8000/user/login/ (note the trailing slash), or set APPEND_SLASH=False in your Django settings.
Django 3.2.8 中，表单的action末尾若未加/ ，会报出上述错误。给出的解决方案👇
Change your form to point to 127.0.0.1:8000/user/login/ (note the trailing slash),
or set APPEND_SLASH=False in your Django settings
APPEND_SLASH 是起什么作用？（默认值是True）
在settings.py里，添加APPEND_SLASH = False ，则不再自动跳转。
把APPEND_SLASH = False注释掉：
需用火狐浏览器。（谷歌浏览器似乎会在自动在url末尾加/）