==================
- When testing ``PURE_PYTHON`` environments under ``tox``, avoid poisoning
the user's global wheel cache.
- Drop support for Python 2.6 and 3.2.
- Add support for Python 3.5 and 3.6.
- Fix `issue 20 <https://github.com/zopefoundation/zope.security/issues/20>`_:
iteration of pure-Python ``BTrees.items()``, and also creating a list from
``BTrees.items()`` on Python 3. The same applies for ``keys()`` and ``values()``.