> the types in question were added to the numeric tower for gmpy 2.0.9 and 2.1.0.

Ah, good to know. Thanks. I was using 2.0.8.

> * We're back to needing a test for the line in question.

Agreed. It's not currently covered, and with the current behaviour the line _is_ necessary.

> * We're eschewing the possibility of changing the behavior of `fractions.Fraction` to force int numerator and denominator.

I think that's a separate issue from this one, and if you want to pursue it it's worth its own issue on the tracker. But there would need to be a good reason for deliberately changing the existing by-design behaviour.