Avoid ISO-8859-1 character in fr.po header.
Adjust make_file override to use binary files only when needed.
Fix REST tests for Python 3.
Fix Python 3 issues in REST code.
Fix issue2550994: breakage caused by configparser backports.
Avoid errors from invalid Authorization headers (issue2550992).
Avoid errors from selecting "no selection" on multilink (issue2550722).
Do not transcode binary email attachments (issue2551004).