MNT: compatibility with newer packaging

[ZLLentz]

I dug into this a bit because newer versions of black and conda require packaging>=22.0.

Following recommendations here: pypa/packaging#631 (comment)
The simplest way to support all versions of packaging is to use the Version class directly instead of the parse function.

parse used to return Version or LegacyVersion depending on if it received a valid version string, but now it raises InvalidVersion instead if the version string is invalid. If we add a try/except around parse then you'll be compatible with packaging>=22 but lose compatibility with packaging<22. Instead, switching to the Version class directly has the same exception raising behavior in all versions of packaging, including the latest.

This seemed like an appropriate fix here because this library only uses LegacyVersion as an indicator that something is a branch rather than a version, so its absence doesn't seem like much of a problem.

closes #27

[goerz]

Looks like it should work in principle, and I'd be happy to merge if you can make the tests pass.

You'll also have to pin black < 23.

[goerz]

It's not going to be that easy… There are several other places where parse_version is called, and I really depend on the old behavior. The easiest fix is probably to backport the entire old parse_version function and the LegacyVersion type (or something that behaves equivalently) into the package.

[ZLLentz]

I didn't realize you were using parse_version elsewhere, that's my bad.

Maybe the easiest thing to do is to use https://pypi.org/project/packvers/ which I think is just a forked/vendored version of packaging at 21.3, or backport/vendor it yourself if you prefer.

[goerz]

I'm going to look into this in #32

[goerz]

Thanks for pointing out packvers! That certainly makes things easy!

[goerz]

I'm going to close this in favor of #32, but I very much appreciate the contribution!

[ZLLentz]

Thank you for moving ahead with this!