这基本上是flask-login版本问题
1.下面这段文字没准能帮到你Posting this here so people can see it, this comes from a change in how UserMixin works in flask-login. I'd tell you to install a specific version of flask-login but...they removed those releases from PyPI.
So...instead of {{ current_user.is_authenticated() }}, you need to use {{ current_user.is_authenticated }}. Just don't include the parentheses. Yeah, it's an annoying change but, honestly, I think it's probably better code design.
2.lask-login的版本问题，flask-login2.x是current_user.is_authenticated(),flask-login3.x是current_user.is_authenticated。避免这个问题最好的办法就是使用虚拟环境并在requirement中写明版本号。
current_user.is_authenticated()基本出现在视图函数(views.py)和模板(templates)里面。