def test_setUnknownVariationSign(self):
        """
        Setting the sign on a heading with unknown variation raises
        C{ValueError}.
        """
        h = base.Heading.fromFloats(1.)
        self.assertIsNone(h.variation.inDecimalDegrees)
        self.assertRaises(ValueError, h.setSign, 1)

        Setting the sign on a heading with unknown variation raises
        C{ValueError}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/positioning/test/test_base.py