fix unit test bug

python/paddle/nn/functional/norm.py

@@ -487,11 +487,11 @@ def local_response_norm(x,
             'Expected 3D or higher dimensionality input, but got {} dimensions'.
             format(dim))
 
-    for i, size in enumerate(sizes):
-        if not size > 0:
+    for i, sz in enumerate(sizes):
+        if not sz > 0:
             raise ValueError("Expected every dim's size to be larger than 0, "
                              "but the size of the {}-th dim is {}".format(i,
-                                                                          size))
+                                                                          sz))
 
     channel_last = True if data_format[-1] == "C" else False