code: function compareDefault (err1, err2) {
  	if (err1.fileName !== err2.fileName) {
  		return (err1.fileName || '').localeCompare(err2.fileName || '');
  	} else if (err1.demote !== err2.demote) {
  		return err1.demote ? 1 : -1;
  	} else if (err1.severity !== err2.severity) {
  		return severity2num(err1.severity) - severity2num(err2.severity);
  	} else if (err1.lineNumber === err2.lineNumber) {
  		return (err1.columnNumber || 0) - (err2.columnNumber || 0);
  	} else {
  		return (err1.lineNumber || 0) - (err2.lineNumber || 0);
  	}
  }
docs: 将错误按照severity>lineNumber>columnNumber这三个维度的优先级排序时，所用的的对象比较函数。
  
  @param {Error} err1 要比较的对象
  @param {Error} err2 要比较的对象
  @returns {int} 比较结果，正数则err1大，负数err2大，0相等