Fix to typo/oversight in python tests

Fix to typo/oversight in python tests, only affecting python 3
diff --git a/python/google/protobuf/internal/reflection_test.py b/python/google/protobuf/internal/reflection_test.py
index 20e5d24..6f3b818 100755
--- a/python/google/protobuf/internal/reflection_test.py
+++ b/python/google/protobuf/internal/reflection_test.py
@@ -636,7 +636,7 @@
     if struct.calcsize('L') == 4:
       # Python only has signed ints, so 32-bit python can't fit an uint32
       # in an int.
-      TestGetAndDeserialize('optional_uint32', 1 << 31, long)
+      TestGetAndDeserialize('optional_uint32', 1 << 31, integer_64)
     else:
       # 64-bit python can fit uint32 inside an int
       TestGetAndDeserialize('optional_uint32', 1 << 31, int)