Avoid stacktrace on process exit in Client.__del__()

[noirbee]

Pull Request check-list

Please make sure to review and check all of these items:

• Do tests and lints pass with this change?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Is there an example added to the examples folder (if applicable)?
• Was the change added to CHANGES file?

NOTE: these things are not required to open a PR and can be done
afterwards / while the PR is open.

Description of change

Client.close() may call ConnectionPool.release() or ConnectionPool.disconnect(); both methods may end up calling os.getpid() (through ConnectionPool._checkpid() or threading.Lock() (through ConnectionPool.reset()). As mentioned in the Python documentation [1], at interpreter shutdown, module globals (in this case, the os and threading module references) may be deleted or set to None before del() methods are called. This causes an AttributeError to be raised when trying to run e.g. os.getpid(); while the error is ignored by the interpreter, the traceback is still printed out to stderr.

Closes #3014

[1] https://docs.python.org/3/reference/datamodel.html#object.__del__

[noirbee]

Note that I unfortunately cannot provide an easy way to reproduce the issue; I can only reproduce it using our own codebase. I suspect this is due to the fact that we load a much larger amount of code than what a synthetic / minimal reproduction attempt would.

[petyaslavova]

Hi @noirbee, thank you for your contribution! I have requested some changes to be added. Once done, I think we will be ready to merge it.

[noirbee]

I have requested some changes to be added.

Thank you for reviewing @petyaslavova , I've updated the code to catch all exceptions and just pass in both Redis and RedisCluster, and rebased on the current master.