'Run the system ``unmount`` tool to unmount this change\'s volume\'s block
device.  The volume must be attached to this node and the corresponding
block device mounted.'

def run(self, deployer, state_persister):

    api = deployer.async_block_device_api
    deferred_device_path = api.get_device_path(self.blockdevice_id)
    def got_device(device):
        UNMOUNT_BLOCK_DEVICE_DETAILS(block_device_id=self.blockdevice_id, block_device_path=device).write(_logger)
        deployer.block_device_manager.unmount(device)
    deferred_device_path.addCallback(got_device)
    return deferred_device_path
