[Checkins] [zopefoundation/Zope] 15f67d: Update to latest bug fix release.

[Michael Howitz]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/Zope
  Commit: 15f67dd3471ca919b1a91a8f429c9f91d61b9607
      https://github.com/zopefoundation/Zope/commit/15f67dd3471ca919b1a91a8f429c9f91d61b9607
  Author: Michael Howitz <mh at gocept.com>
  Date:   2019-06-17 (Mon, 17 Jun 2019)

  Changed paths:
    M constraints.txt
    M requirements-full.txt
    M versions-prod.cfg

  Log Message:
  -----------
  Update to latest bug fix release.