Catch different failure modes of subprocess.run
Add default versions of NIXOS_CONFIGURATION and
HOME_MANAGER_CONFIGURATION to compare to env vars, assume
configuration is a flake if different and append "--flake" argument to
process commands
Combine unnecessary amount of python files into single main.py
Add default.nix for building without Flakes enabled
Adjust flake.nix to use poetry2nix callPackage for both default and
shell, to be more consistent