add ci for pypy3

[DorianGray]

This adds(readds?) testing of qtile with pypy3

[DorianGray]

It looks like github actions does not support pypy3.7 (7.3.3) yet. This will have to hold until it does.

[ramnes]

Looks like they heard you! This PR got merged a few hours ago: actions/setup-python#168

pypy-3.7 should work now, if I understand correctly.

[DorianGray]

Lets see if it works!

[tych0]

Most of these failures look "legit" (aka someone needs to spend some time with the test suite & pypy3 and figure them all out). Given that it works in cpython, I can't imagine there's anything too awful, just a bunch of fiddly stuff.

This matches my understanding of the state of affairs: we had "allowed failure" testing of pypy3 in travis-ci, which basically meant it always failed and nobody paid attention to it :)

[DorianGray]

oof, ok. I'll take a look at these as I go and fix what I can then.

[ramnes]

Can we close this PR meanwhile?