Python tests: pytest and asserts
I am going to switch Python test suite from unittest to pytest. This is going to enable us to use `assert` instead of the dreadful `assertEqual` like so. If assertion fails, pytest report shows actual values on both sides of the equation. I will also use a regex to convert current code to new style. I am posting this for everyone to see, asking that anyone writing new tests, respect this style.
```py3
        self.assertEqual(r.ltr.as_int, 12345678)
        assert r.ltr.as_int == 12345678
```
