- Don't explicitly prevent the ``timeout`` from being lower than the
  ``reissue_time`` when setting up an ``AuthTktAuthenticationPolicy``
  (previously such a configuration would raise a ``ValueError``, now it's
  allowed, although typically nonsensical).  Allowing the nonsensical
  configuration made the code more understandable and required fewer tests.

- Add a test for when the auth_tkt value is empty.