Sorry for not thinking of trying this sooner. Running garbage collection, import gc; gc.collect(), releases the resources and restores the expected reference counts.

From my perspective, this is satisfactory and could justify closing this bug report. 

The exception logic in Enum.__new__ could potentially be cleaned up for this use case, just not sure if that would introduce risk for other use cases. 

I am guessing (from the perspective of the larger Python exception handling design and implementation) what this bug report demonstrates had been previously thought through.