The unknown-8bit trick was designed to deal with unknown bytes in an
ASCII message, and it works fine for that. However, I also tried to
extend it to handle bytes that can't be decoded using the charset
specified in an encoded word, and there it fails because there can be
other non-ASCII characters that were *successfully* decoded. The fix is
simple: do the unknown-8bit encoding using the utf-8 codec. This is
especially appropriate since anyone trying to do recovery on an unknown
byte string will probably attempt utf-8 first.
(cherry picked from commit 1e17ccd030)
Co-authored-by: R. David Murray <rdmurray@bitdance.com>
Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>