I created a new tool, lucaswerkmeister-wmde-test, with a very basic Flask app that shows whether it has a SECRET_KEY from the config or not. After some false starts and debugging, I eventually figured out how to load the config file correctly (it’s best to pass an absolute file into app.config.from_file(); don’t change the working directory or Flask’s root_path) and updated the documentation a bit. Changing the Python version worked very well for me (though you have to be aware of which Python versions Heroku supports – not any point version!).

I also discovered T337025: Unknown error when trying to delete a Toolforge build during this ^^

For local testing, I also figured out how to run pack via Docker (and added that to the docs too) because the CNCF’s PPA is only available for LTS Ubuntu releases – but I didn’t end up using this very much in the end. (Pulling all the images over the conference wifi was slow!)