def get_installed_pypackages():
    return {p.project_name.lower(): p for p in pkg_resources.working_set}
def test_exceptions(self):
        self.assert_(issubclass(DeoptionError, TypeError))
        self.assertRaises(TypeError,
            lambda: Optional()
        )
        self.assertRaises(TypeError,
            lambda: Optional(NotPassed, NotPassed)
        )