Make FGM work for exotic dtypes. Some black-ing, pep8-ing. Fix broken…

… test.

cleverhans/torch/tests/test_attacks.py

@@ -489,6 +489,7 @@ def test_clips(self):
             if norm == 1:
                 self.assertRaises(
                     NotImplementedError,
+                    self.attack,
                     model_fn=self.model,
                     x=self.normalized_x,
                     eps=0.3,