title: Disable simultaneous login from multiple different places on Flask-Login
body: <p>I have a Web service written in <a href="http://flask.pocoo.org/" rel="noreferrer">Flask</a>. User A uses some username to log in to the service. I want it to be impossible for user B to log in using the same username, until user A's session is expired. In other words, I want to disable concurrent, simultaneous logins per user. How do I do that in <a href="https://flask-login.readthedocs.org/en/latest/" rel="noreferrer">Flask-Login</a>?</p>