Capture warning in test_sys

Author: brianschubert

Lib/test/test_sys.py

@@ -1877,7 +1877,8 @@ def test_pythontypes(self):
         check = self.check_sizeof
         # _ast.AST
         import _ast
-        check(_ast.AST(), size('P'))
+        with self.assertWarns(DeprecationWarning):
+            check(_ast.AST(), size('P'))
         try:
             raise TypeError
         except TypeError as e: