code: function formatLine({ rule, message, location }, metrics) {
    const { line, col } = location;
    const { line: lineW, col: colW, message: msgW } = metrics;
    const loc = sprintf(`%${lineW}d:%-${colW}d`, line, col);
    const msg = sprintf(`%-${msgW}s`, message);
    return `  ${loc}  ${msg}  ${rule}`;
  }
docs: Formats the output line with the widths given in `metrics`
  
  @private
  @param {{
  rule: string,
  message: string,
  location: parse5.LocationInfo
  }} error
  @param {{line: number, col: number, message: number}} metrics
  @return {string}