fdo#70796 fix quoted printable encoding bug in internal Python

Change-Id: I4e5563c47df83c50df75ccf330fbd38ec6da9170
Reviewed-on: https://gerrit.libreoffice.org/7437
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>