- Add patch to fix build with new zope.interface:
* tests.patch

- version update to 4.6.3
- Fix a crash in the test suite under a 32-bit CPython on certain
32-bit platforms. See `issue 137
`_. Fix by
`Jerry James `_.
- Fix an ``AssertionError`` clearing a non-empty ``PersistentMapping``
that has no connection. See `issue 139
`_.

- update to 4.6.1
* Stop installing C header files on PyPy
* Fix slicing of PersistentList to always return instances of the same class.
* Fix copying of PersistentList and PersistentMapping using copy.copy
to also copy the underlying data object.
* Update the handling of the PURE_PYTHON environment variable.
* Add preliminary support for Python 3.9a3+.
* Fix the Python implementation of the PickleCache to be able to
store objects that cannot be weakly referenced.
* Add support for Python 3.8.