Fix Python 2

Author: leezu

tests/python/unittest/test_gluon.py

@@ -1515,14 +1515,14 @@ def forward(self, x):
 def test_save_load_deduplicate_with_shared_params():
     class B(mx.gluon.Block):
         def __init__(self, params=None):
-            super().__init__(params=params)
+            super(self, B).__init__(params=params)
 
             with self.name_scope():
                 self.weight = self.params.get('weight', shape=(10, 10))
 
     class C(mx.gluon.Block):
         def __init__(self, b1, b2):
-            super().__init__()
+            super(self, C).__init__()
             self.b1 = b1
             self.b2 = b2