function _fnLog(settings, level, msg, tn) {
		msg = 'DataTables warning: ' +
			(settings ? 'table id=' + settings.sTableId + ' - ' : '') + msg;

		if (tn) {
			msg += '. For more information about this error, please see ' +
				'https://datatables.net/tn/' + tn;
		}

		if (!level) {
			// Backwards compatibility pre 1.10
			var ext = DataTable.ext;
			var type = ext.sErrMode || ext.errMode;

			if (settings) {
				_fnCallbackFire(settings, null, 'dt-error', [settings, tn, msg], true);
			}

			if (type == 'alert') {
				alert(msg);
			}
			else if (type == 'throw') {
				throw new Error(msg);
			}
			else if (typeof type == 'function') {
				type(settings, tn, msg);
			}
		}
		else if (window.console && console.log) {
			console.log(msg);
		}
	}
Log an error message
 @param {object} settings dataTables settings object
 @param {int} level log error messages, or display them to the user
 @param {string} msg error message
 @param {int} tn Technical note id to get more information about the error.
 @memberof DataTable#oApi