const_missing

# File activesupport/lib/active_support/json/encoding.rb, line 149
        def const_missing(name)
          if name == :CircularReferenceError
            message = "The JSON encoder in Rails 4.1 no longer offers protection from circular references. "                        "You are seeing this warning because you are rescuing from (or otherwise referencing) "                        "ActiveSupport::Encoding::CircularReferenceError. In the future, this error will be "                        "removed from Rails. You should remove these rescue blocks from your code and ensure "                        "that your data structures are free of circular references so they can be properly "                        "serialized into JSON.\n\n"                        "For example, the following Hash contains a circular reference to itself:\n"                        "   h = {}\n"                        "   h['circular'] = h\n"                        "In this case, calling h.to_json would not work properly."

            ActiveSupport::Deprecation.warn message

            SystemStackError
          else
            super
          end
        end