void sendErrorPacket(IQ packet, PacketError.Condition error, Element pubsubError) {
        IQ reply = IQ.createResultIQ(packet);
        reply.setChildElement(packet.getChildElement().createCopy());
        reply.setError(error);
        if (pubsubError != null) {
            // Add specific pubsub error if available
            reply.getError().getElement().add(pubsubError);
        }
        router.route(reply);
    }
Generate a conflict packet to indicate that the nickname being requested/used is already in
use by another user.

@param packet the packet to be bounced.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/PubSubEngine.java