method_missing

# File railties/lib/rails/railtie/configuration.rb, line 99
      def method_missing(name, *args, &blk)
        if name.end_with?("=")
          key = name[0..-2].to_sym
          if actual_method?(key)
            raise NoMethodError.new("Cannot assign to `#{key}`, it is a configuration method")
          end
          @@options[key] = args.first
        elsif @@options.key?(name)
          @@options[name]
        else
          super
        end
      end