… And its working!! 
I had read the pinned post regarding 4.26 & Python 3+ and briefly wondered if that had anything to do with it but as 4.26 was released Dec 20 and the thread was started Mar 21 I wrongly assumed not and dismissed it.
not calling it in Python was exactly the kind of oversight I feared I was making but im ecstatic my EditorUtility is now up and running.
@UE_FlavienP Thank you for your timely reply and kindly pointing out my error.
and
@Rayvneye Thank you for posting the updated code in the first place!
much appreciated!