Modernize Python support

[chuckwondo]

Many versions of Python have been released (and many have become unsupported) since this repo was first created, and there are at least a couple of places where I've noticed either an unspecified minimum required Python version, or code that is meant to accommodate some very old Python versions.

For example, the classifiers block in pyproject.toml does not list any specific Python versions. I suggest this block be updated appropriately, including a minimum no less than Python 3.8. In fact, the GitHub Actions workflows use only 3.10 or later, so these should likely also be enhanced to perform a matrix of tests across all versions of Python this library is intended to work with (perhaps 3.8 through 3.12, with 3.13 to follow soon).

One place in the code attempts to accommodate a very old package structure for urllib functionality that should be simplified/unified. There may be other places that should be modernized, but maybe not. The codebase is relatively small, but I haven't looked for other spots yet.

[frankinspace]

Yes I agree. Just a few more points to add.

With poetry the minimum python version supported is defined here:
https://github.com/nasa/python_cmr/blob/develop/pyproject.toml#L15
If you tried to pip install with anything less than 3.8 you would get an error. But I agree, with 3.8 EOL set for October this year this library should have the minimum version increased. I'd be on board with supporting 3.10, 11, and 12.

The CI for this library uses 3.10 for build and test:
https://github.com/nasa/python_cmr/blob/develop/.github/workflows/python-app.yml#L18-L22
Also, very much in support of setting up a matrix build for multiple python versions. I have done this before and it is not too challenging (example: https://github.com/podaac/data-subscriber/blob/7c3895d973c0d9840476220aab7dc50ad526b130/.github/workflows/python-app.yml#L13-L31) but I don't have time at this moment to work on that (bring on the PRs! :) )

Also, very supportive of removing code that is no longer necessary as we upgrade the python version.

[chuckwondo]

@frankinspace, thanks for the follow up on the issues I recently created. I fully intend to submit PRs for them all (unless someone beats me to them). I'm going to start with this one since I think it's perhaps the most fundamental one to address.