The CI has a “Build Docker image and store in cache step”.
That step executes docker buildx build [..] --tag exercism/TRACK_SLUG-analyzer.
Docker complains, Error: buildx failed with: ERROR: invalid tag "exercism/TRACK_SLUG-analyzer": repository name must be lowercase. See this build for example.
I created a PR which replaces TRACK_SLUG with track_slug.
This repo did not previously contain track_slug anywhere so this should not have any unintended matching side effects.