Hi @alexharvey, thank you for getting that PR. Unfortunately, 3 weeks is not a long time in the span it takes for engineering to respond to PRs on the repo. I have added it into the list of PRs for the team to look at, though... strange that I didn't respond on the ticket (I try to when I'm doing that).
It would be great if this is an easy solve, but I think the issue is that the public packages are not the correct versions to test against. All of the Puppet Core releases need authentication (or should, unless something has changed).