'``detach_volume`` raises ``UnattachedVolume`` if the supplied
``blockdevice_id`` is not attached to a host.'

def test_detach_detached_volume(self):

    volume = self.api.create_volume(dataset_id=uuid4(), size=self.minimum_allocatable_size)
    exception = self.assertRaises(UnattachedVolume, self.api.detach_volume, volume.blockdevice_id)
    self.assertEqual(exception.args, (volume.blockdevice_id,))
