Don't store a RichHandler object in the argparse namespace (#3394)

[cpitclaudel]

Resolves: #3394

• Ensured tests pass and (if applicable) updated functional test output
• Conformed to code style guidelines by running appropriate linting tools
• Added tests for changed code
• Updated documentation for changed code

Unfortunately I can't test locally, but this patch should be harmless, at least.

[snh]

I too was getting the error described in #3394 and can confirm this patch fixes the issue for me.

[justinmayer]

Thanks, Clément! Do you think it's worth adding a test that fails for MacOS images in CI when this change is not present?

[cpitclaudel]

A regression test would be nice, yes. I suppose the best way to go about it would be to start the file watcher and then stop it a few seconds later somehow, asserting that it didn't crash in the meantime? I don't know when I'll have the time to do that.