…ound (pythonGH-122233)GH-GH- Encode header parts that contain newlinesPer RFC 2047:> [...] these encoding schemes allow the> encoding of arbitrary octet values, mail readers that implement this> decoding should also ensure that display of the decoded data on the> recipient's terminal will not cause unwanted side-effectsIt seems that the "quoted-word" scheme is a valid way to includea newline character in a header value, just like we already allowundecodable bytes or control characters.They do need to be properly quoted when serialized to text, though.GH-GH- Verify that email headers are well-formedThis should fail for custom fold() implementations that aren't carefulabout newlines.(cherry picked from commit0976339)Co-authored-by: Petr Viktorin <encukou@gmail.com>Co-authored-by: Bas Bloemsaat <bas@bloemsaat.org>Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>