PPermut: Raise a StopIteration when all permutations are complete

Author: ideoforms

examples/ex-permut-degree.py examples/ex-permutations.pyexamples/ex-permut-degree.py renamed to examples/ex-permutations.py

@@ -401,7 +401,7 @@ def __next__(self):
             self.pos = 0
 
         if self.permindex >= len(self.permutations):
-            return None
+            raise StopIteration
 
         rv = self.permutations[self.permindex][self.pos]
         self.pos += 1