This wanted to the *.typelib files in some sort of x86_64-lib or something, which was causing python3.7 to
not find the files.

However, this probably isn't a part of a matched set of py gi releases.

Also, I -suspect- it was causing py gi to give top-level windows that are totally blank, as though
they were doing the right things, but invisibly; buttons were still clickable.

I tried both gprog and notify-when-up2 - both gave plain white windows with clickable buttons.

I also tried alt-f2 r. It did not help. I was using Mint 19.1 with Cinnamon at the time.