Only test size with Python 3.7

Author: ekilmer

tests/other/test_smtlibv2.py

@@ -127,10 +127,10 @@ def check(ty: Type, pickle_size=None, sizeof=None, **kwargs):
                 not hasattr(x, "__dict__"),
             )
             """
-            self.assertEqual(len(pickle_dumps(x)), pickle_size)
             if sys.version_info[1] == 6:  # Python 3.6
                 self.assertEqual(sys.getsizeof(x), sizeof)
             elif sys.version_info[1] == 7:  # Python 3.7
+                self.assertEqual(len(pickle_dumps(x)), pickle_size)
                 self.assertEqual(sys.getsizeof(x), sizeof + 8)
             elif sys.version_info[1] >= 8:  # Python 3.8+
                 self.assertEqual(sys.getsizeof(x), sizeof - 8)