Add support for PyPy

[ngnpope]

Supersedes #62.

This seemed to be enough to get everything passing on PyPy 3.10.

[dvarrazzo]

If we add support for pypy, do we need to add trove classifiers to the metadata? To the pool too?

[dvarrazzo]

We would also need to add an entry to the supported systems docs and to docs/news.rst

[ngnpope]

I've pushed up two fixup commits, the first with all the general bits and the second is focused on the gc stuff.

[dvarrazzo]

Hello,

this is largely good! I have squashed the second commit into the first, did some minor cleanup, and also rebased on the 3.1 maintenance branch. If everything is good I will release psycopg 3.1.14 in a few hours, with pypy support.

Thank you very much!

[dvarrazzo]

There was a surprising error in psycopg 3.1 on pypy 3.9, which didn't appear in psycopg master nor on pypy 3.10. I think that the problem is just an anyio 3 bug (master uses anyio 4) so I've skipped the failing tests.

Psycopg 3.1.14 is on the way!

[ngnpope]

Thanks Daniele!

[dvarrazzo]

Thank you, @ngnpope!

Package released! Thank you for the help, and of course testing is welcome!

[om26er]

Did we get around to doing any performance benchmarks? Would be great to know.