------------------
Bug fixes:
- Fix Unauthorized error due to importing six inside Restricted Python
`Plone issue 2463 <https://github.com/plone/Products.CMFPlone/issues/2463>`_
[davilima6]
- Migrate Tests away from PloneTestCase
[pbauer]
- Do not run webdav_history.txt in py3 since it breaks tests (no webdav support in py3).
[pbauer]
- cleanup: isort/formatting/security decorators
[jensens]
- InitializeClass was moved to AccessControl.class_init - use it.
[jensens]
- setDefaultRoles is deprecated.
addPermission from AccessControl.Permission is instead used.
[jensens]