code: function lineMetrics(errors) {
    const initialValues = { message: 0, line: 0, col: 0 };
  
    return errors.reduce((vals, { message, location: { line, col } }) => (
      { message: Math.max(vals.message, message.length),
        line: Math.max(vals.line, line.toString().length),
        col: Math.max(vals.col, col.toString().length),
      }
    ), initialValues);
  }
docs: Calculates the maximum width of each of the line, col, and message
  parts of the error output, e.g.:
  
  @private
  @example
  const errors = [
  { message: 'This message has 30 characters',
  location: { line: 100, col: 5 },
  },
  { message: 'This has 17 chars',
  location: { line: 2, col: 20 },
  };
  ];
  
  lineMetrics(errors);
  // => { message: 30, line: 3, col: 2 }
  
  @param {Linter.LinterError[]} errors
  @return {{line: number, col: number, message: number}}