Hmm? I must have misunderstood the test. Here's my understanding: the test is testing that a an object ref only held in the traceback object of the exception is cleaned up such that it can be collected. In a refcount system that collection is immediate, in a gc world its after the next gc run.

Ah, perhaps the test was flawed to start with, since no effort is made in it to capture the error and then process it. If we pass a result in, the traceback will have a ref and gc.collect() can't possibly be discarding the entire structure.