… threadIf `Py_IsFinalizing()` is true, non-daemon threads (other than the current one)are done, and daemon threads are prevented from running, so theycannot finalize themselves and become done. Joining them without timeoutwould block forever.Raise PythonFinalizationError instead of hanging.Seegh-123940 for a use case: calling `join()` from `__del__`. This isill-advised, but an exception should at least make it easier to diagnose.