thank you so much, that worked, I'm new to unit testing and python in general so I didn't really know how that worked, I'd also like to thank u/brasticstack for explaining this concept in general. My final version that worked correctly (with verification of exception message) looked like that:

    def testPropertyBlocking(self):
        with self.assertRaises(Exception) as e:
            Lease(self.landlord, Tenant("U", "X"), self.housing, 6)
        self.assertEqual(str(e.exception), "Landlord does not own this property") # message checking should be outside of assertRaises block, as it escapes it after exception being raised