BLD: unvendor meson-python on 1.26.x and upgrade to meson-python 0.15

[rgommers]

This is a backport of gh-25008. It closes gh-25681.

[rgommers]

The Windows wheel build failures showing Invalid --only='""' are due to an issue with cibuildwheel pypa/cibuildwheel#1740. Upgrading to fix that.

[rgommers]

The other issue is in the regular musllinux job:

$ /__w/numpy/numpy/test_env/bin/python -m pytest --rootdir=/__w/numpy/numpy/build-install/usr/lib/python3.10/site-packages -n auto -m 'not slow' numpy
/__w/numpy/numpy/test_env/lib/python3.10/site-packages/_pytest/config/__init__.py:328: PluggyTeardownRaisedWarning: A plugin raised an exception during an old-style hookwrapper teardown.
Plugin: helpconfig, Hook: pytest_cmdline_parse
ConftestImportFailure: ImportError: Error importing numpy: you should not try to import numpy from
        its source directory; please exit the numpy source tree, and relaunch
        your python interpreter from there. (from /__w/numpy/numpy/build-install/usr/lib/python3.10/site-packages/numpy/conftest.py)
For more information see https://pluggy.readthedocs.io/en/stable/api_reference.html#pluggy.PluggyTeardownRaisedWarning
  config = pluginmanager.hook.pytest_cmdline_parse(
ImportError while loading conftest '/__w/numpy/numpy/build-install/usr/lib/python3.10/site-packages/numpy/conftest.py'.
numpy/__init__.py:135: in <module>
    raise ImportError(msg) from e
E   ImportError: Error importing numpy: you should not try to import numpy from
E           its source directory; please exit the numpy source tree, and relaunch
E           your python interpreter from there.

Looks like that is due to a new pluggy version (1.4.0, released last week) - yay for transitive dependencies: matplotlib/pytest-mpl#221. It's almost holiday time for me, so I'm inclined to just ignore that for now on 1.26.x, since it's harmless.

[charris]

since it's harmless.

The wheels look to be built and pass, which is my main concern, but I suspect that is a bit of an accident, perhaps because pytest is pinned to 7.4.0 in test_requirements and those requirements are installed before running the wheel tests. Alternatively, the wheel tests are -mfast, while the musl tests are -m 'not slow'.

In any case we may want to look at numpy/conftest.py, which has

#FIXME when yield tests are gone.
@pytest.hookimpl()
def pytest_itemcollected(item):

We still have yield tests. Scipy doesn't have the hook, so that is good.

[charris]

Thanks Ralf.