small py2 fixes, port to py3 and enable & apply fixes for GitlabCI
Why draft:
- Can someone with org access to TMWA add an attobuild repo copied from https://git.themanaworld.org/specing/attobuild so that the submodule link can be updated to no longer refer to my personal repo?
I have squashed what was sensible from my perspective. If you would prefer the full, 32 commit version, say so, and I may bring it out of reflog.