The version of PyPy3 that's provisioned is quite old (and buggy -- e.g. PyYAML doesn't even seem to work on it on Windows -- https://github.com/Julian/github-actions-test/runs/205309060#step:5:29 )

The current version is a Python 3.6 (https://www.pypy.org/download.html#building-from-source) and a lot more stable (I'm not sure whether it fixes the YAML issue above but going to check, it probably should).

(Not sure whether the PyPy2 is also out of date, I can't tell yet how to check its version without writing a build to just output it -- also not sure if this is something I can fix myself and send a PR for but if I do see how to do that will be sure to.)