I got it on my own by implementing the following IQProvider:
publicclass HarmonyHubResponseIQProvider implements IQProvider{
public IQ parseIQ(XmlPullParser parser) throws Exception {
String errorCode = parser.getAttributeValue(null, "errorcode");
String errorMessage = parser.getAttributeValue(null, "errorstring");
String content = parser.nextText();
returnnew HarmonyHubResponseIQ(errorCode, errorMessage, content);
}
}