[Checkins] [zopefoundation/zope.sendmail] c39720: Work with messages as bytes (#29)

[Viktor Dick]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/zope.sendmail
  Commit: c397206f35fd2e7e7c40e99d5edc406f9d697baa
      https://github.com/zopefoundation/zope.sendmail/commit/c397206f35fd2e7e7c40e99d5edc406f9d697baa
  Author: Viktor Dick <viktordick at users.noreply.github.com>
  Date:   2020-07-24 (Fri, 24 Jul 2020)

  Changed paths:
    M src/zope/sendmail/delivery.py
    M src/zope/sendmail/queue.py
    M src/zope/sendmail/tests/test_delivery.py
    M src/zope/sendmail/tests/test_queue.py

  Log Message:
  -----------
  Work with messages as bytes (#29)

This is based on the discussion in
`https://github.com/zopefoundation/Products.MailHost/issues/30`
and
`https://github.com/zopefoundation/Products.MailHost/pull/32`.

In order to allow messages with 8bit-encoding to be sent using smtplib,
they have to be prepared as bytes. Since any preparation and header
parsing and manipulation is done in `Products.MailHost`, `zope.sendmail`
only needs to store messages internally as bytes and allow them to be
passed as bytes.

Co-authored-by: dieter <dieter at handshake.de>