Update art/attacks/evasion/pixel_threshold.py

Author: beat-buesser

art/attacks/evasion/pixel_threshold.py

@@ -483,6 +483,7 @@ def _perturb_image(self, x: np.ndarray, img: np.ndarray) -> np.ndarray:
 
 class CMAEarlyStoppingException(Exception):
     """Raised when CMA is stopping early after successful optimisation."""
+
     pass