mail: add type hints for pytype...
mail: add type hints for pytype
We essentially annotate functions in which handling of bytes/str is not
obvious in order to hopefully clear things out. See also changeset
2ade00f3b03b introducing typing hints in Mercurial.
Most types are straightforward but a few is wrong, and we need to
either disable pytype on respective instructions or use wrong
annotations. These will be fixed in next changesets. Notice the type
Union[bytes, str] of "s" parameter of headencode(), this reflects how
email.header.Header.append() behaves.
