Corrected test

[radarhere]

Instead of raising the Exception at https://github.com/python-pillow/Pillow/blob/master/src/PIL/TiffImagePlugin.py#L484 as intended, this test was raising a NameError because ImageFileDirectory_v2 is not imported.

[hugovk]

Good spot, asserting against Exception is a bit too general.

Should we also assert the exception message to be sure it's the right one?

    def test_set_legacy_api(self):
        ifd = TiffImagePlugin.ImageFileDirectory_v2()
        with self.assertRaises(Exception) as e:
            ifd.legacy_api = None
        self.assertEqual(str(e.exception),
                         "Not allowing setting of legacy api")

[radarhere]

Okay, sure, I've updated the commit with your code.

[hugovk]

The AppVeyor failure is unrelated, I've created #3156 for that.