[PATCH] events.signup.blacklisted not shown properly

Summary

"events.signup.blacklisted" is not properly displayed when a blacklisted person tries to register for an event. Instead, events.signup.failed is shown

Additional Debug Information

Confirmed on powerpc64le-linux-gnu

$ chromium --version
Chromium 70.0.3538.67 built on Debian buster/sid, running on Debian bullseye/sid

and x86_64-pc-linux-gnu

$ firefox --version
Mozilla Firefox 82.0.3

Patch

Attached is a patch that fixes the bug (or at least I think it does, I didn't want to figure out how to server the website) amiv-website.diff

PS: Can I get unblacklisted for fixing this? :)