[Checkins] [zopefoundation/z3c.form] 4451dc: Fixed Python 3.7/3.8 datetime tests.

[Maurits van Rees]

  Branch: refs/heads/maurits/3x-update-python-versions
  Home:   https://github.com/zopefoundation/z3c.form
  Commit: 4451dc70eb1e4cd1f3b3cac84cbfc39064489782
      https://github.com/zopefoundation/z3c.form/commit/4451dc70eb1e4cd1f3b3cac84cbfc39064489782
  Author: Maurits van Rees <maurits at vanrees.org>
  Date:   2020-08-28 (Fri, 28 Aug 2020)

  Changed paths:
    M src/z3c/form/converter.txt

  Log Message:
  -----------
  Fixed Python 3.7/3.8 datetime tests.

Cherry-picked from e4eb6fd79bfae77391d7e7625ed5b65543c6f9dc.