[Checkins] [zopefoundation/zope.testrunner] e04cb4: There's no reason to use private unittest classes

[GitHub]

  Branch: refs/heads/py36
  Home:   https://github.com/zopefoundation/zope.testrunner
  Commit: e04cb435cbaebf6a4a8b16b1884d03e0a2c60f0d
      https://github.com/zopefoundation/zope.testrunner/commit/e04cb435cbaebf6a4a8b16b1884d03e0a2c60f0d
  Author: Marius Gedminas <marius at gedmin.as>
  Date:   2016-12-28 (Wed, 28 Dec 2016)

  Changed paths:
    M src/zope/testrunner/runner.py
    M src/zope/testrunner/tests/testrunner-unexpected-success.txt

  Log Message:
  -----------
  There's no reason to use private unittest classes

The only reason to import _UnexpectedSuccess is to format an exception
message, and we can use any class we want for that.