config_when_updating

# File railties/lib/rails/generators/rails/app/app_generator.rb, line 89
    def config_when_updating
      cookie_serializer_config_exist = File.exist?('config/initializers/cookies_serializer.rb')

      config

      unless cookie_serializer_config_exist
        gsub_file 'config/initializers/cookies_serializer.rb', /json/, 'marshal'
      end
    end