bug#52071: gajim 1.3.3 fails to build

[bdju]

guix system
guix (GNU Guix) d48b404cf577cbfcd29b294e193a4db0c3e580b1
http://ix.io/3FVJ log here

lines of note:
```
ImportError: Failed to import test module: gajim_mocks
ModuleNotFoundError: No module named 'gajim.gui.emoji_data'
```