Fun - I don't think I've ever used Pants to run tests on pypy, but it worked (almost) seamlessly! Just required setting the repo-wide default constraints to empty, so that we don't try to merge CPython and PyPy constraints...

I often feel guilty burning so many trees in the Pex CI on PyPy2 and PyPy3 shards to support this, but that's been the point! I'm glad this works as intended.