Comment 1 for bug 1513667

I've encountered this as well, it appears that juju is confused about leader status, since this is a single unit but this is the only thing in the logs. Note that this starter, as far as I can tell, spontaneously, I wasn't logged on to the unit nor was anyone else interacting with it.

2015-12-04 06:45:02 WARNING juju.worker.uniter.operation leader.go:115 we should run a leader-deposed hook here, but we can't yet
2015-12-04 06:45:04 ERROR juju.worker.uniter.filter filter.go:137 tomb: dying
2015-12-04 06:45:04 WARNING juju.worker.dependency engine.go:304 failed to start "uniter" manifold worker: dependency not available
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That message repeats up until the current time.