http://python-future.org/compatible_idioms.html

# Python 2 and 3
s1 = u'The Zen of Python'
s2 = u'きたないのよりきれいな方がいい\n'
-------------------------------^^ <-- should be '\n'

s2 = u'きたないのよりきれいな方がいいx\n'
-------------------------------^^ <-- insert 'x': OK

FLTK 1.4 w/pango, git commit e18de6ff0306
Date:   Sat Feb 22 07:15:08 2020 +0100

OS: Linux Mint 19.2 (based on Ubuntu)