Add some features to restricted python and fix problems revealed by running Zope's test suites.

Bug fixes

Disallow access to old style classes without security declarations. This is not allowed in vanilla zope, but we allowed this accidentally about two years ago. This branch includes some fixes for cases where we accessed not protected classes in a way that should not have been allowed - ERP5 test suite pass, but there might be more cases in code not covered by ERP5 test suite.
Fix iterating on reversed(iterable) which was unauthorized, maybe since python 2.7
Disallow new style classes in container access (iteration, {}.get etc). Only classes had this problem, not instances, so this probably has no impact for us, but it allows running AccessControl test suite.
Disallow attribute names ending in __roles__ in class name. This probably does not impact us either, but also for AccessControl tests suite.

New features

Allow iterating on a generator. It's still not possible to use yield statement in restricted python, but iterating is now possible
Allow cStringIO.StringIO("initial value"), only cStringIO.StringIO() was allowed
Enable collections.namedtuple and add a few tests for other members of collections ( not collections.deque because we never used it so far )

Edited Apr 03, 2020 by Jérome Perrin