Visual feedback when the login fails

[fengelniederhammer]

On staging, the login is currently failing for me, but I don't get any useful feedback. I just see failed requests with 403 in the browser dev tools. Add something that says that something went wrong.

[fengelniederhammer]

What happens actually when the login fails? Is it worth to display a pop up? Let's find out. Maybe we also need better error handling (clearing cookies, deleting a cache, then try again the redirect?)?