Raise AssertionError when coordinates parameter is invalid

[redfrexx]

Raise AssertionError when coordinates parameter is invalid, e.g. when a list of strings is passed instead of coordinate tuples.

This should raise an AssertionError:

    coordinates = [("1", "1"), ("1", "2"), ("2", "2"), ("2", "1"), ("1", "1")]
    my_poly = MyPolygon(coordinates)

[redfrexx]

Read here how to test whether an exception is raised using pytest.