Making isinstance fail (in a customizable way)

Question

I'm trying to write a regression test for a Python C extension that "forgot" to check for failures for PyObject_IsInstance. But the only thing I could come up with was a metaclass that overrides __instancecheck__, for example:

import six

class InstanceCheckGoneWrong(type):
    def __instancecheck__(self, other):
        raise TypeError('isinstance failed')

@six.add_metaclass(InstanceCheckGoneWrong)
class FailingIsinstanceClass():
    pass

It works:

>>> isinstance(1, FailingIsinstanceClass)
TypeError: isinstance failed

But it seems very complicated. Is there an easier way (python2 and python3 compatible) to let PyObject_IsInstance (isinstance) fail? A customizable exception would be best, but a builtin would also do.