Note that as far as I'm aware, AIX doesn't actually provide any of our coercion target locales yet, so the question in my previous comment is about how we want 3.7.x releases to behave on AIX if IBM *do* introduce a C.UTF-8 locale.

The main argument I see in favour of leaving locale coercion enabled is that the latin-1 default will cope with UTF-8 encoded data from Python 3.7+ applications (even if it displays them incorrectly), but may raise UnicodeEncodeError if an application attempts to create arbitrary Unicode filenames, or write arbitrary unicode data to the standard streams.