Python Version Deprecations for 0.9.12 about pygsti

[rileyjmurray]

With CVXPY, our policy is that we can drop support for a version of Python without warning if the Python Software Foundation drops support for that version. Since the PSF dropped support for 3.7 a while back I'd say there's good cause to drop it from pyGSTi's supported Python versions.

[sserita]

In that case, maybe we can just accelerate our timeline and drop 3.7 as of 0.9.12. I'll experimentally turn on testing for Python 3.11 and see how bad it is - if just a few more straggling changes, we can do that this release also.

[sserita]

Completely agree - let's plan to deprecate 3.7 in release 0.9.12, and then drop 3.7 and add 3.11 for release 0.9.13. I think at this point we've got many of the main bugs with 3.11, but I'm sure the tests will catch a few more.

Is there an easy way to indicate python version deprecation? Maybe @rileyjmurray knows this? In the past, I think we have just dropped and added Python version support with no warning, but we can always strive to do better. Obviously I can include the deprecation in the release notes and on the PyPi page, but that seems to have limited exposure.

[sserita]

Closed with release of 0.9.12.