In Setuptools 72.0.0, `setuptools.command.test` was temporarily removed.
This version of Setuptools was yanked, and 72.1.0 restored the
functionality (it appears that the removal didn't follow the standard
process, but this functionality has been deprecated for many years).

The functionality will be removed in a future version (probably very
soon) and that would break this `setup.py` as a result.

This commit, as a first step, handles the `ImportError` that results
when `setuptools.command.test` is removed, and only attempts to define
the `PyTest` command (the only thing depending on it) when it's
available.

For more details, please see:

pypa/setuptools#4519

Although many projects were affected by the change, this one was the
unlucky "winner" of a popular Stack Overflow Q&A drawing attention to
the general issue:

https://stackoverflow.com/questions/78806100

A `pyproject.toml` file is created to represent project metadata,
following the standards laid out in PEP 621 and implemented by modern
Setuptools:

https://peps.python.org/pep-0621/

Data which can be represented this way, and which is not specific to the
Setuptools build system, has been moved across and removed from the
`setup` keyword arguments.

Add spaces around equals signs, and use double-quotes for strings.
This is the standard formatting for TOML that will be output by typical
tools (although the other way is also valid).

`pyproject.toml` can also do basic configuration of Setuptools for
building packages, as shown. Note that `include-package-data` is set as
`True` by default when using `pyproject.toml`.

With the modern approach using `pyproject.toml`, it's not actually
necessary to call `setup` to build the project, as long as all necessary
information for wheel building is in `pyproject.toml` (which it is now).

Therefore, the script now immediately bails out whenever
`setuptools.command.test` is not available, and uses a minimal `setup`
invocation when it is.

Going forward, it is strongly recommended to remove `setup.py` entirely.
A `setup.py` file is only required for projects that need to build
extensions or have some other compelling reason to execute arbitrary
code at build time. The interface implemented here - i.e. calling
`setup.py test` - is deprecated, and has been for many years.

Instead, consider using a shell alias to make the desired command (i.e.
`python -m pytest --strict-markers --verbose --tb=long`) easier to use.

For more details, please see:
https://setuptools.pypa.io/en/latest/deprecated/commands.html