Clean installation only worked after downgrading

[javicarron]

I was preparing a new environment with a clean installation using the latest versions, python=3.13.0 and cython=3.0.11. The installation script was failing the classy compilation throwing a ModuleNotFound error (for Cython), but import cython was working fine when I tried on a Python session of this same environment.

I eventually solved it by downgrading to cython=0.29.37, which in turn required a downgrade of python=3.12. The installation seems to be working as expected with these versions (at numpy=2.1.3).

This downgrade is not a problem to me, so feel free to close the issue. But I figured it may be relevant given that there seemed to be some problems upgrading to the newest versions of numpy and cython, so I leave it here if it is useful.

Thank you very much for your work!