Import ActionController::MissingRenderer from Rails

lib/action_controller/responder.rb

@@ -3,6 +3,15 @@
 require "active_support/json"
 
 module ActionController # :nodoc:
+  unless defined?(:MissingRenderer)
+    # See Responder#api_behavior
+    class MissingRenderer < LoadError
+      def initialize(format)
+        super "No renderer defined for format: #{format}"
+      end
+    end
+  end
+
   # Responsible for exposing a resource to different mime requests,
   # usually depending on the HTTP verb. The responder is triggered when
   # <code>respond_with</code> is called. The simplest case to study is a GET request: