If you can somehow cleanly pass in the <code>test</code object's <code>tmp_dir</code> attribute, the directory path it stores is automatically cleaned up by the test harness.  Then you won't need to override <code>__del__</code> which has a non-obvious side-effect: It run's asynchronously in the garbage collector, so can create evil, bad, hard to find race-conditions.

But if it's a major pain, don't worry about it, it's okay to override this, we just need to be careful.