gh-117783: Immortalize objects that use deferred reference counting by colesbury · Pull Request #118112 · python/cpython

My intention was to keep the fields alive, but maybe that's not the best way to address this.

Basically, test_concurrent_futures.test_interpreter_shutdown was failing because a weakref was cleared later than usual, after the module dictionary was partially cleared. I was concerned that the problem might not be limited to that test, but I don't really have evidence for that one way or the other.

I'll get rid of this swapping and make the weakref callback more robust.