Welcome to PokéCommunity! Register now and join one of the best fan communities on the 'net to talk Pokémon and more! We are not affiliated with The Pokémon Company or Nintendo.
Thanks, and by the way, running it from any directory other than the project's root causes a FileNotFoundError. So more like:
$ cd subscript
$ python3 gui.py
Users of Ubuntu-based distros will need to install these packages:
python3-gi
gir1.2-gtksource-3.0
gir1.2-gtkspell3-3.0
gir1.2-clutter-1.0
You might want to include this info in the original post, because the package names that Ubuntu uses aren't quite obvious.