Serhiy is right, Condition.wait() has the following code:

        finally:
            # Must reacquire lock even if wait is cancelled
            cancelled = False
            while True:
                try:
                    await self.acquire()
                    break
                except exceptions.CancelledError:
                    cancelled = True

            if cancelled:
                raise exceptions.CancelledError

It swallows CancelledError exceptions from waiters and re-raises CancelledError without the cancellation message.