The bug reporter merely copies the incorrect error that gitlab gave him; The issue here is that someone working in login / security of gitlab doesn't know what

The bug reporter merely copies the incorrect error that gitlab gave him; The issue here is that someone working in login / security of gitlab doesn't know what a mime type is. That is extremely worrying - it's not a part of the code where you can afford to be sloppy. It's a very odd error. Apparently .nro is a file extension used by the Nintendo Switch video game console; .o is obviously the output of compilers, so I'm not sure why my username wasn't rejected. Maybe it would be if I tried to register now.