old_contents: // ESLint Configuration Files enables to include comments.
  // http://eslint.org/docs/configuring/#comments-in-configuration-files
  module.exports = {
      'env': {
          'node': true,
          'mocha': true
      }
  };
new_contents: 'use strict';
  
  // ESLint Configuration Files enables to include comments.
  // http://eslint.org/docs/configuring/#comments-in-configuration-files
  module.exports = {
      'env': {
          'node': true,
          'mocha': true
      }
  };
  
subject: fix errors