I created a python package at tools/python-kde-release, included a Bash script helper to run commands from the Python package (including transparently creating or updating a virtual environment), and created an add_bugzilla_versions.sh Bash script in the root of this repository that uses the helper Bash script to run the corresponding Python method.
If the approach seems OK to everyone, I can proceed to do the same with the appstream script, and implement proper code sharing in the process.