Test the error message

Author: vstinner

Lib/test/test_capi/test_type.py

@@ -15,7 +15,8 @@ class MyType:
         MyType.attr = "mutable"
 
         type_freeze(MyType)
-        with self.assertRaises(TypeError):
+        err_msg = "cannot set 'attr' attribute of immutable type 'MyType'"
+        with self.assertRaisesRegex(TypeError, err_msg):
             # the class is now immutable
             MyType.attr = "immutable"
 
@@ -36,7 +37,6 @@ class D(A, C): pass
         # as well
         type_freeze(D)
 
-
     def test_freeze_meta(self):
         """test PyType_Freeze() with overridden MRO"""
         type_freeze = _testcapi.type_freeze