[Checkins] [zopefoundation/Zope] 1f539f: Add support for Python 3.9.

[Michael Howitz]

  Branch: refs/heads/support-python3.9
  Home:   https://github.com/zopefoundation/Zope
  Commit: 1f539fffc5e9850ea220e8806a5604d20cc40098
      https://github.com/zopefoundation/Zope/commit/1f539fffc5e9850ea220e8806a5604d20cc40098
  Author: Michael Howitz <mh at gocept.com>
  Date:   2020-10-07 (Wed, 07 Oct 2020)

  Changed paths:
    M CHANGES.rst
    M buildout.cfg
    M constraints.txt
    M requirements-full.txt
    M setup.py
    M versions-prod.cfg

  Log Message:
  -----------
  Add support for Python 3.9.