[Checkins] [zopefoundation/zExceptions] ec9224: Use `str(self)` as detail if it is not set.

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/zExceptions
  Commit: ec9224f81c7d8e149ac50a372b042753eff5cbfb
      https://github.com/zopefoundation/zExceptions/commit/ec9224f81c7d8e149ac50a372b042753eff5cbfb
  Author: Hanno Schlichting <hanno at hannosch.eu>
  Date:   2016-09-08 (Thu, 08 Sep 2016)

  Changed paths:
    M CHANGES.rst
    M src/zExceptions/__init__.py
    M src/zExceptions/tests/test___init__.py

  Log Message:
  -----------
  Use `str(self)` as detail if it is not set.