old_contents: 'use strict';
  
  module.exports = {
      'env': {
          'es6': true,
      },
      'ecmaFeatures': {
          'modules': true,
      },
      'rules': {
          // Require let or const instead of var
          'no-var': [2],
      },
  };
  
new_contents: 'use strict';
  
  module.exports = {
      'env': {
          'es6': true,
      },
      'ecmaFeatures': {
          'modules': true,
      },
      'rules': {
          // Require braces as-needed around arrow function bodies
          'arrow-body-style'       : [2, 'as-needed'],
          // Require parentheses around arrow function arguments as-needed
          'arrow-parens'           : [2, 'as-needed'],
          // Require space before/after arrow function’s arrow
          'arrow-spacing'          : [2],
          // Disallow use of this/super before calling super() in constructors
          'no-this-before-super'   : [2],
          // Disallow unnecessary computed property keys on objects
          'no-useless-computed-key': [2],
          // Disallow unnecessary constructors
          'no-useless-constructor' : [2],
          // Require let or const instead of var
          'no-var'                 : [2],
          // Require arrow functions as callbacks
          'prefer-arrow-callback'  : [2],
          // Require const declarations for variables that are never reassigned after declared
          'prefer-const'           : [2],
          // Require spread operators instead of .apply()
          'prefer-spread'          : [2],
          // Require template literals instead of string concatenation
          'prefer-template'        : [2],
          // Require rest parameters instead of arguments
          'prefer-rest-params'     : [2],
          // Disallow spacing between rest and spread operators and their expressions
          'rest-spread-spacing'    : [2, 'never'],
          // Disallow spacing around embedded expressions of template strings
          'template-curly-spacing' : [2, 'never'],
      },
  };
  
subject: Enable more core “ES6” rules