Allowed NBRT on Mac/Lin but warned & non-default + char encoding work

Known issue: I can't figure out how to get ARKO's translation fixes,
namely to the accent characters that are extended, to work reliably
on Windows Command Prompt (or PowerShell... only cygwin will ever
do the right thing).  I've tried pure UTF-8, pure Windows-1252,
pure ISO-8859-1 (Latin-1).  None of them give consistent results.
To top it off, it also depends upon how Python itself interprets
the characters (as indicated by the -*- coding: latin-1 -*- directive
at the top of the file), of which I've tried all the possible combos.

Text-based UIs suck, in other words.  At least ones that aren't UTF-8
aware such as cygwin.