def test_detach_unknown_volume(self):
        blockdevice_id = self.unknown_blockdevice_id
        exception = self.assertRaises(
            UnknownVolume,
            self.api.detach_volume, blockdevice_id=blockdevice_id
        )
        self.assertEqual(exception.args, (blockdevice_id,))
``detach_volume`` raises ``UnknownVolume`` if the supplied
dataset/ETHPy150Open ClusterHQ/flocker/flocker/node/agents/testtools/_blockdevice.py/IBlockDeviceAPITestsMixin.test_detach_unknown_volume