Use status, content_type, body method signature for render too

actionpack/lib/action_dispatch/middleware/public_exceptions.rb

 module ActionDispatch
-  # A simple Rack application that renders exceptions in the given public path.
   class PublicExceptions
     attr_accessor :public_path
 
@@ -12,15 +11,15 @@ def call(env)
       status       = env["PATH_INFO"][1..-1]
       request      = ActionDispatch::Request.new(env)
       content_type = request.formats.first
-      format       = content_type && "to_#{content_type.to_sym}"
       body         = { :status => status, :error => exception.message }
 
-      render(status, body, format, content_type)
+      render(status, content_type, body)
     end
 
     private
 
-    def render(status, body, format, content_type)
+    def render(status, content_type, body)
+      format = content_type && "to_#{content_type.to_sym}"
       if format && body.respond_to?(format)
         render_format(status, content_type, body.public_send(format))
       else