@Override
    public OpenstackNode removeNode(String hostname) {
        checkArgument(!Strings.isNullOrEmpty(hostname), ERR_NULL_HOSTNAME);
        OpenstackNode osNode = osNodeStore.removeNode(hostname);
        log.info(String.format(MSG_NODE, hostname, MSG_REMOVED));
        return osNode;
    }
@Test(expected = IllegalArgumentException.class)
    public void testRemoveNullNode() {
        target.removeNode(null);
    }