Pkg-about

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- Setup (dependencies) update.

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- Setup update (now based on tox >= 4.0).
- Cleanup.

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- Add support for Python 3.12
- Drop support for Python 3.7
- Add support for PyPy 3.10
- Drop support for PyPy 3.7 and 3.8
- Bugfix for parsing metadata's "Project-URL".
- Bugfix of about_from_setup() for __version_info__.
- | Enhancement" the 'package_path' parameter of the about_from_setup()
| can now be of type string or Path.
- Bugfix of about_from_setup() for parsing author and maintainer emails.
- Copyright year update.
- Added a trivial unit test.

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- Tox configuration has been moved to pyproject.toml

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- Setup update.

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- Add __author_email__ (as alias of __email__).
- Add __maintainer_email__.
- Setup update (currently based mainly on pyproject.toml).