I can't seem to get this to work as intended.
Anyone can feel free to take over.

I can't seem to get this to work as intended. Anyone can feel free to take over.

It's working! Now the tests are failing "successfully", i.e., it reproduces the build error seen in other repositories that depend on this package.

It is my guess, that with the new build procedure (using the build library), if a new version is published, the accompanying binary wheel that will be uploaded should fix the installation issues for dependent packages - however, this is merely a guess and could be wrong.
BUT it can be tested by the new CI test introduced in this branch by simply creating a new release and then rerunning the CI tests here, checking and ensuring the newest version is fetched from PyPI, specifically for the CI - Build package / herokuish-build (pypi) job.

While tests seem to pass now it doesn't mean it's working as intended, unfortunately. Especially considering I cannot locate the templates in the template folders for Voilà and NBConvert. This means the post_install() function is not being run by pip install, which is bad.
Another solution needs to be made - either manually copying over the template by any users of the template or similar. This particular pathway can be made easier by making the post_install() functionality available through a command line script or similar.