Yes, it is a deliberate choice. It is difficult to explain why it was passed without it -- dues to a specific order of calling tearDown() and callbacks registered with addCleanup() in different base classes.

Using an event object would fix it too, but:

* Re-using an existing event object (like self.done) can have side effects in future.
* Introducing a new event object has a risk of name conflicts, because the hierarchy of classes is complicated, and same name can be reused by accident.
* time.sleep() is already used in other similar tests for timeouts. We only need to do a sleep longer then the timeout on the client side (0.01).

Given all this, I decided that adding time.sleep(1) was the simplest, the most obvious, and maybe the most resistant to future human errors way. If we want to use an event object here, we will need to re-consider using time.sleep() in other tests.

What comment do you want to add?