Add pypy wheels

[rth]

It would be nice if PyPy wheels could be build for scipy. This was recently done for numpy in MacPython/numpy-wheels#74 by @mattip

Because scipy takes quite a while to build from sources for downstream packages building wheels e.g. with cibuildwheel (which includes pypy by default) that would also save a lot of compilation time.

[tylerjereddy]

Interesting. We had PyPy builds in our (SciPy) regular CI for a while, although they were a regular source of maintenance burden and eventually removed. Even for NumPy, I believe that PyPy in regular CI requires a bit of Matti's expertise to keep "green."

Not saying it won't happen--just providing the brief context on where we are with PyPy at the moment. I suspect adding back to our main repo CI would be needed as pre-requisite to providing wheels--otherwise the release manager gets a lot of "fun" when they try to build the pypy wheels for SciPy :)

[pv]

A Pypy dev has a repo building Pypy wheels for a number of packages including scipy here: https://github.com/antocuni/pypy-wheels

[stonebig]

PyPy did some progress and is now at Python-3.8 compatibility, maybe is it worth a retry ?

[lesshaste]

+1 for this.

[mattip]

Since the wheel builds are now done via scipy/scipy with cibuildwheel, this issue should be transferred there.

[rgommers]

I just tried, but transferring issues is only possible within a single GitHub organization. So we should open a new issue there with a summary of this one, and then comment here so everyone subscribed can follow the new issue. Any takers?

[mattip]

I opened scipy/scipy#17974 and will close this one.