flask中在模板中使用current_user.is_authenticated，运行报错，提示没定义
报错信息
Traceback (most recent call last):
File "E:PythonPython35-32libsite-packagesflaskapp.py", line 2000, in __call__
return self.wsgi_app(environ, start_response)
File "E:PythonPython35-32libsite-packagesflaskapp.py", line 1991, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "E:PythonPython35-32libsite-packagesflaskapp.py", line 1567, in handle_exception
reraise(exc_type, exc_value, tb)
File "E:PythonPython35-32libsite-packagesflask\_compat.py", line 33, in reraise
raise value
File "E:PythonPython35-32libsite-packagesflaskapp.py", line 1988, in wsgi_app
response = self.full_dispatch_request()
File "E:PythonPython35-32libsite-packagesflaskapp.py", line 1641, in full_dispatch_request
rv = self.handle_user_exception(e)
File "E:PythonPython35-32libsite-packagesflaskapp.py", line 1544, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "E:PythonPython35-32libsite-packagesflask\_compat.py", line 33, in reraise
raise value
File "E:PythonPython35-32libsite-packagesflaskapp.py", line 1639, in full_dispatch_request
rv = self.dispatch_request()
File "E:PythonPython35-32libsite-packagesflaskapp.py", line 1625, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "D:1filepythontestloglog.py", line 90, in login
return render_template("/login.html", form=form)
File "E:PythonPython35-32libsite-packagesflaskemplating.py", line 134, in render_template
context, ctx.app)
File "E:PythonPython35-32libsite-packagesflaskemplating.py", line 116, in _render
rv = template.render(context)
File "E:PythonPython35-32libsite-packagesjinja2environment.py", line 989, in render
return self.environment.handle_exception(exc_info, True)
File "E:PythonPython35-32libsite-packagesjinja2environment.py", line 754, in handle_exception
reraise(exc_type, exc_value, tb)
File "E:PythonPython35-32libsite-packagesjinja2\_compat.py", line 37, in reraise
raise value.with_traceback(tb)
File "D:1filepythontestlogemplateslogin.html", line 1, in top-level template code
{% extends "base.html"%}
File "D:1filepythontestlogemplatesase.html", line 1, in top-level template code
{% extends "bootstrap/base.html" %}
File "E:PythonPython35-32libsite-packagesflask_bootstrapemplatesootstrapase.html", line 1, in top-level template code
{% block doc -%}
File "E:PythonPython35-32libsite-packagesflask_bootstrapemplatesootstrapase.html", line 4, in block "doc"
{%- block html %}
File "E:PythonPython35-32libsite-packagesflask_bootstrapemplatesootstrapase.html", line 20, in block "html"
{% block body -%}
File "E:PythonPython35-32libsite-packagesflask_bootstrapemplatesootstrapase.html", line 21, in block "body"
{% block navbar %}
File "D:1filepythontestlogemplatesase.html", line 12, in block "navbar"
{% if current_user.is_authenticated %}
File "E:PythonPython35-32libsite-packagesjinja2environment.py", line 408, in getattr
return getattr(obj, attribute)
jinja2.exceptions.UndefinedError: 'current_user' is undefined
