Convert to Python 3: `object.next` -> `object.__next__`

tests/test_hoover.py

@@ -380,7 +380,7 @@ class CartmanTest(unittest.TestCase):
             def __iter__(self):
                 return self
 
-            def next(self):
+            def __next__(self):
                 try:
                     item = self.items[self.n]
                 except IndexError: