Login with user without "Superuser" rights doesn't work

If you login (e.g. another family member) with its user that is "active" and could also be "admin" but lacks "superuser" rights, login simply doesn't work. Errors are thrown - see attached screenshot. It sure is expected to work also for users who don't have superuser rights.

Hello Mr Kaffee, 

I will take a look into that. 

Thanks
Björn