gevent 1.5.0 will no longer install about gevent HOT 1 CLOSED

I strongly recommend you use a current gevent version. gevent 1.5 does not support Python 3.9 or newer. There are absolutely things that it gets wrong on those newer versions that it is unaware of. That's the reason you have to compile it: 3.9 and newer aren't supported and there were never any binary wheels for them.

That said, I think you're running into issues with a newer Cython version. You'll need to set a pip constraint to get an older version of Cython; the version that gevent 1.5 was tested with was 0.29.14, but note that that version doesn't support Python 3.10 --- Python 3.10 was tested with 3.0a9 but that version won't compile gevent 1.5. There may be a 0.X.X release that can handle newer Python versions and also compile gevent 1.5 code, but I've never tested that and I have no idea what version that would be.

$ echo 'cython<3' > /tmp/constraints.txt
$ PIP_CONSTRAINT=/tmp/constraints.txt pip install gevent==1.5

Good luck.

from gevent.