Log Message:
py-ZopeInterface: updated to 5.1.2

5.1.2 (2020-10-01)
==================

- Make sure to call each invariant only once when validating invariants.
  Previously, invariants could be called multiple times because when an
  invariant is defined in an interface, it's found by in all interfaces
  inheriting from that interface.  See `pull request 215
  <https://github.com/zopefoundation/zope.interface/pull/215/>`_.

5.1.1 (2020-09-30)
==================

- Fix the method definitions of ``IAdapterRegistry.subscribe``,
  ``subscriptions`` and ``subscribers``. Previously, they all were
  defined to accept a ``name`` keyword argument, but subscribers have
  no names and the implementation of that interface did not accept
  that argument. See `issue 208
  <https://github.com/zopefoundation/zope.interface/issues/208>`_.

- Fix a potential reference leak in the C optimizations. Previously,
  applications that dynamically created unique ``Specification``
  objects (e.g., used ``@implementer`` on dynamic classes) could
  notice a growth of small objects over time leading to increased
  garbage collection times. See `issue 216
  <https://github.com/zopefoundation/zope.interface/issues/216>`_.

  .. caution::

     This leak could prevent interfaces used as the bases of
     other interfaces from being garbage collected. Those interfaces
     will now be collected.

     One way in which this would manifest was that ``weakref.ref``
     objects (and things built upon them, like
     ``Weak[Key|Value]Dictionary``) would continue to have access to
     the original object even if there were no other visible
     references to Python and the original object *should* have been
     collected. This could be especially problematic for the
     ``WeakKeyDictionary`` when combined with dynamic or local
     (created in the scope of a function) interfaces, since interfaces
     are hashed based just on their name and module name. See the
     linked issue for an example of a resulting ``KeyError``.

     Note that such potential errors are not new, they are just once
     again a possibility.