Use importlib.metadata (pygal requires 3.8+)

[akx]

Fixes #545 (comment)

importlib_metadata from PyPI is only required for Python < 3.8; importlib.metadata is always available on 3.8+, and the minimum python_requires here is 3.8+ (01649cb).

Regressed in d1d02c6

[akx]

cc @gentooboontoo :)

[gentooboontoo]

Thanks @akx. Unfortunately importlib.metadata API changed in Python 3.10.

Unless I am wrong, using importlib_metadata allows to use the latest API with Python < 3.10 (see #545 (comment) and compatibility notes). The dependency will be dropped once support for Python 3.9 is discontinued.

[akx]

@gentooboontoo Shouldn't tests catch that? I'm currently on mobile so I can't see whether CI has run here.

[akx]

(Back from lunch.) Oh, there is no CI that would run here... I can make a PR to fix that first made a PR to fix that: #549.

[akx]

Okay, never mind – until targeting Python 3.10+, using importlib-metadata from PyPI is probably an okay idea.

See https://pypi.org/project/backports.entry-points-selectable/.