def render_404_template!(template_name)
      VIEW_TEMPLATE_ENGINES.each do |engine, extension|
        @preferred_extension = extension.to_s
        find_template(settings.views, template_name, engine) do |file|
          next unless File.file?(file)
          halt send(extension, template_name.to_sym, layout: false)
        end
      end
    end
def render_404_template!(template_name)
      VIEW_TEMPLATE_ENGINES.each do |engine, extension|
        @preferred_extension = extension.to_s
        find_template(settings.views, template_name, engine) do |file|
          next unless File.file?(file)
          halt send(extension, template_name.to_sym, layout: false)
        end
      end
    end
Given a template name, and with a prioritized list of template engines, attempts to render a
 404 template, if one exists, and halt.

 @param [String] template_name
 @see VIEW_TEMPLATE_ENGINES