report the key of xml parser registration object

alib2xml/src/core/xmlApi.hpp

@@ -105,11 +105,12 @@ private:
 public:
 	template < class Type >
 	static void unregisterXmlReader ( ) {
-		if ( ! parseFunctions ( ).erase ( xmlApi < Type >::xmlTagName ( ) ) ) {
+		const std::string & tagName = xmlApi < Type >::xmlTagName ( );
+		if ( ! parseFunctions ( ).erase ( tagName ) ) {
 			std::string groupName = ext::to_string < object::Object > ( );
 			std::string typeName = ext::to_string < Type > ( );
-			throw::exception::CommonException ( "Parse callback of " + typeName + " not registered in group " + groupName + "." );
+			throw::exception::CommonException ( "Parse callback of " + typeName + " identified as " + tagName + " not registered in group " + groupName + "." );
 		}
 	}