bpo-44666: Use default encoding as fallback for compile_file (GH-27236)

When sys.stdout.encoding is None compile_file will fall back to
sys.getdefaultencoding to encode/decode error messages.

Co-authored-by: Stefan Hoelzl <stefan.hoelzl@posteo.de>
Co-authored-by: Mickaël Schoentgen <contact@tiger-222.fr>