Add __about__.py providing package metadata such as __version__

[bernhardkaindl]

It is common that python packages export package.__version__:

• Provide it for version identification so it can be logged by projects using this package.
• Other package metadata could be provided by it as well.
• Update setup.py to read the version for single-sourcing the version.
• Add test case testing package.__version__ and setup.py --version

A complete description is in sdbus_async/networkmanager/__about__.py

[bernhardkaindl]

Hi @igo95862, thanks for #14, I'd like to check and show the package version in my project so I'd like to add package.__version__ which many packages provide too.

[igo95862]

I looked if this was somehow standardized and this is what I found.

https://peps.python.org/pep-0396/#pep-rejection

It looks like the __version__ attribute was a draft at some point but got rejected.

The proper way of querying the package version is importlib.metadata.version

The package.__version__ is not going to break anything but I need to think about adding it.

[bernhardkaindl]

https://peps.python.org/pep-0396/#pep-rejection

Yes, while it was rejected, many many packages use it.

The proper way of querying the package version is importlib.metadata.version

This is only available with python >=3.8, but since I use at least 3.8, that's ok for me, works and no additional code.

Users of 3.7 have pkg_resources.get_distribution('sdbus-networkmanager').version (which is said to be slow) and the backport importlib_metadata for 3.7. So, ok with me.