Currently I'm working on packaging for NixOS again after someone else made some headway.
I've gotten tests to run, with some workarounds, as per NixOS/nixpkgs#64047 (comment)

Could you patch build.py to append to - instead of overwriting PYTHONPATH?
This is needed because build.py calls the test runner, which needs PYTHONPATH set correctly on NixOS, due to our use of nonstandard FHS.

If there's any other env vars treated similarly it might be good to fix them too.