Fix test for new exception.

Author: skion

tests/test_jwt.py

@@ -385,7 +385,7 @@ def test_encode_decode_with_algo_none(self):
         jwt_message = jwt.encode(self.payload, key=None, algorithm=None)
 
         self.assertRaises(
-            NotImplementedError,
+            jwt.DecodeError,
             lambda: jwt.decode(jwt_message))
 
         jwt.decode(jwt_message, verify=False)