[PySide] Problem promoting a custom widget in QtDesigner

[henry.wede at yahoo.com]

 Hello,
After a couple frustrating days with the QGraphicsView and QGraphicsScene, I have most of the hard stuff done.  Or so I thought...  I need to deal with scaling the scene when the size of the window changes.  I found a working example at this link:
https://stackoverflow.com/questions/63543338/resizing-qgraphicsscene-when-layout-changes
The bottom example on that page does what I need it to do.  Except that it lays out the widgets manually and I use QtDesigner for everything because the applications can become large and it is much easier.  So then I looked into promoting my QGraphicsView into a custom widget.  That is when I hit a wall.
After making the change in QtDesigner, it looks like this:



At the bottom of the UI file it seems to have the correct filename and class name for the custom widget.  And the class seems to be "inserted" correctly.




But when I run the program, it displays a rather unhelpful message and reverts back the normal widget


The attached files should duplicate what I have described.

Can somebody please tell me how to promote these widgets properly?
Thank you in advance,Henry 
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