This project is derived from https://github.com/tutsplus/Flask-LDAP-Auth-Demo, but I updated several things that no longer work in the original project.
First, Flask-Login's AnonymousUserMixin uses properties like AnonymousUserMixin.is_authenticated, instead of a is_authenticated() method call in the original project
Next, the LDAP server had to be changed to reflect a service that is still online. I also trapped another LDAP exception (ldap.SERVER_DOWN) in the login view.
Go to ldapflask/__init__.py and customize settings for your environment. You probably also need to change try_login() in ldapflask/auth/models.py and make the LDAP path reflect your specific environment.