The system on which I encountered the test failure uses ncurses 5.7, so that's consistent with the theory that the test is tickling an ncurses bug.

I'll have a look at testing with ncurses 5.8, but it is not available from RedHat or CentOS (and it never will be for the current and past versions of those systems), so that's not a good solution for most users.

On the other hand, it's not clear to me how serious is the bug revealed by the test failures, nor whether there is any viable workaround on the Python side.