[Checkins] [zopefoundation/Persistence] 1edd17: Try out Python 3.9

[Michael Howitz]

  Branch: refs/heads/py39
  Home:   https://github.com/zopefoundation/Persistence
  Commit: 1edd177789fb8982e9e86ab5eb7d3478e1150791
      https://github.com/zopefoundation/Persistence/commit/1edd177789fb8982e9e86ab5eb7d3478e1150791
  Author: Michael Howitz <mh at gocept.com>
  Date:   2020-02-11 (Tue, 11 Feb 2020)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Try out Python 3.9