DeprecationWarnings with Python 3.11a1

[icemac]

What I did:

tox -e py311

What I expect to happen:

Successful run without deprecation warnings.

What actually happened:

Successful run (yeah!) but a load of deprecation warnings like this:

.../lib/python3.11/unittest/case.py:646: DeprecationWarning: It is deprecated to return a value!=None from a test case (<bound method InterfaceConformanceTestsMixin.test_class_conforms_to_iface of <zope.schema.tests.test__bootstrapfields.BoolTests testMethod=test_class_conforms_to_iface>>)
  return self.run(*args, **kwds)

The reason seems to be:

zope.schema/src/zope/schema/tests/test__bootstrapfields.py

Lines 43 to 57 in 9378f5a

	def test_class_conforms_to_iface(self):
	from zope.interface.verify import verifyClass
	cls = self._getTargetClass()
	__traceback_info__ = cls
	for iface in self._getTargetInterfaces():
	verifyClass(iface, cls)
	return verifyClass
	def test_instance_conforms_to_iface(self):
	from zope.interface.verify import verifyObject
	instance = self._makeOne()
	__traceback_info__ = instance
	for iface in self._getTargetInterfaces():
	verifyObject(iface, instance)
	return verifyObject

Those methods are used in some child classes for super calls but in others they are not overwritten.

What version of Python and Zope/Addons I am using:

Python 3.11a1 on master of zope.schema.