[Checkins] [zopefoundation/Zope] 81ac80: Add support for Python 3.9. (#908)

[Michael Howitz]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/Zope
  Commit: 81ac8054c210b7d25d9e572d0648b789e99ae73d
      https://github.com/zopefoundation/Zope/commit/81ac8054c210b7d25d9e572d0648b789e99ae73d
  Author: Michael Howitz <mh at gocept.com>
  Date:   2020-10-08 (Thu, 08 Oct 2020)

  Changed paths:
    M .travis.yml
    M CHANGES.rst
    M buildout.cfg
    M constraints.txt
    M docs/migrations/index.rst
    A docs/migrations/zope5.rst
    M docs/news.rst
    M docs/roadmap.rst
    M requirements-full.txt
    M setup.py
    M versions-prod.cfg

  Log Message:
  -----------
  Add support for Python 3.9. (#908)

* Garden documentation.
* Add a bit of migration documentation.