Adopt cython3 (require >=3)

[pp-mo]

🚀 Pull Request

Description

[pp-mo]

@trexfeathers I think this may possibly be all that is needed ?

So far, this adopts exactly what Bill proposed :

• insist on Cython>=3
• remove the "language_level" setting.

But .. I'm still not sure it wouldn't be better to simply unpin Cython, and leave the language-level explicit (which is then not superfluous).

Particularly as I see that the build does raises a warning about the default having changed recently.
/Users/runner/work/cf-units/cf-units/.tox/py311-osx-test/lib/python3.11/site-packages/Cython/Compiler/Main.py:381: FutureWarning: Cython directive 'language_level' not set, using '3str' for now (Py3). This has changed from earlier releases! File: /Users/runner/work/cf-units/cf-units/cf_units/_udunits2.pxd

What do you think ?

[pp-mo]

Updated to enable macos-14 (hopefully 🤞 )

[pp-mo]

Updated to enable macos-14 (hopefully 🤞 )

Initial attempt got a failure from setuptools-scm, which failed to identify the version.
On closer inspection of the log, it seems to be a github access timeout.

But it fails again on retry. Can't easily work out whether it is essentially a timeout, or maybe a timeout due to something else failing.

[pp-mo]

Updated again to pick up the git-path fix (i.e. #464)
Hopefully that gives a solid pass (where before it seemed variable with lots of re-spins)