Choose the right Python version (3.6.0) and remove print from last line, simply return.

I had the same problem of using the new string formatting convention I was going to do something like this (pseudocode follows)

return f'{max function here} {min function here}'

and it kept complaining. I think their python version they use to run the tests might be older (pre 3.6?).

Not a kata issue, marking as resolved.

As for your issue, I don't know enough Python to answer you. Maybe someone else here can?