Remove cython from installation

[tiagocoutinho]

Cython should only be necessary during build.
Installations should stay cython free (current version of cython alone takes 20MB)

[tiagocoutinho]

This was not doing anything that fixes installation without cython installed.
The real fix was on pyproject.toml by adding cython as build dependency

[Erotemic]

I think this is correct.

[erezsh]

I wonder what it means. Maybe the version needs to be bumped?

[Erotemic]

Maybe the error is a CI hickup and needs to be rerun? Or by updating to actions/upload-artifact@v4, maybe its doing a duplicate name check that was previously silently overwriting data?

[tiagocoutinho]

I think you're right @Erotemic.
I had a look at update-artifact@v4 changes.
Looks like they added a merge artifact sub-action.
I've updated the PR with what I think are the needed changes

[Copilot]

Pull Request Overview

This PR removes Cython from runtime installation requirements and ensures it’s only used at build time, and it updates CI workflow steps to use the latest artifact action versions and revised wheel-building patterns.

• Always import cythonize and drop Cython from install_requires
• Restrict Cython to setup_requires
• Bump actions/upload/download-artifact to v4 and adjust wheel-skip patterns

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
setup.py	Removed fallback import and Cython from install_requires, now only in setup_requires
.github/workflows/tests.yml	Updated upload/download artifact actions to v4, renamed sdist artifact, and refined skip patterns

Comments suppressed due to low confidence (3)

.github/workflows/tests.yml:47

• [nitpick] The artifact name "wheels-src" is misleading for a source distribution; consider renaming it to "sdist" or "source-dist" for better clarity.

        name: wheels-src

.github/workflows/tests.yml:135

• This download step only fetches merged wheel artifacts; the sdist artifact ("wheels-src") isn’t downloaded, so the source distribution won’t be available downstream. Add a separate download-artifact step for the sdist.

      uses: actions/download-artifact@v4

setup.py:33

• The use of setup_requires is deprecated by modern pip; consider moving the Cython build requirement into a pyproject.toml under [build-system] as recommended by PEP 518.

    setup_requires=["Cython>=3.0,<3.1"],

[tiagocoutinho]

Please let me know if you need anything else from my side

[erezsh]

Thanks for the PR!