FIX #1836 - polylabel runs into infinite loop with tiny polygon

[djm93dev]

I believe this should fix issue #1836

[jorisvandenbossche]

Thanks for the PR! And sorry for the slow reply .. Could you add a test for this? (I think you can take the example from the bug report for that, and add a test based on that in test_polylabel.py)

[jorisvandenbossche]

And it also seems to actually change the result (failing test, didn't look further into how the result is different):

    def test_polylabel(self):
        """
        Finds pole of inaccessibility for a polygon with a tolerance of 10
    
        """
        polygon = LineString(
            [(0, 0), (50, 200), (100, 100), (20, 50), (-100, -20), (-150, -200)]
        ).buffer(100)
        label = polylabel(polygon, tolerance=10)
        expected = Point(59.35615556364569, 121.8391962974644)
>       assert expected.equals_exact(label, 1e-6)
E       assert False
E        +  where False = <bound method BaseGeometry.equals_exact of <POINT (59.356 121.839)>>(<POINT (57.906 108.751)>, 1e-06)
E        +    where <bound method BaseGeometry.equals_exact of <POINT (59.356 121.839)>> = <POINT (59.356 121.839)>.equals_exact

shapely/tests/legacy/test_polylabel.py:21: AssertionError