Packaging mcomix3 (python, gtk): Missing gsettings schemas issue

I’m trying to package mcomix3 and got pretty far, as in the application starts, but crashes in a few dialogs with the message:

Gib-GIO-ERROR **: 09:54:45.625: No GSettings schemas are installed on the system

Here are my and @AndersonTorres efforts so far:

I’ve found this in the python FAQ: NixOS - Nixpkgs 21.05 manual but despite what the FAQ item says, adding gsettings-desktop-schemas doesn’t tell me what’s actually missing, error remains the same. There is a schema file in the mcomix3 repo but no idea what to do with it. @worldofpeace offered their help in the original issue, but I suspect they are very busy.

IIRC gsettings schemas are affected by the same issue as gobject-introspection:

Try adding strictDeps = false.

We should really mention it with the other setup hooks too, since it affect almost every one of them.

Thanks, I’m carefully optimistic that actually solved the problem. Although I’m feeling like this:

I made my first PR. Care to review, @jtojnar?