Unfortunately, this is a side effect of using an AttributeProxy in JobContainer. The autospec mocks the proxy, meaning that anything that is normally proxied will just throw AttributeErrors.

Seeing as doing it this way doesn't actually rely on the proxy behavior that's a part of JobContainer, I'll make the test a bit tighter by doing `self.job_container.manual_start = self.job_container.job_scheduler.manual_start` instead, and then setting `self.job_container.manual_start.return_value`.