HTTPError help you to create your own 404, 500 and/or 501 response

To create a custom 404 reponse, create a fonction HTTPError.r404 in your application :

  module Capcode
    class HTTPError
      def r404(f)
        "#{f} not found :("
      end
    end
  end

Do the same (r500, r501, r403) to customize 500, 501, 403 errors