Add some more tests

Author: sergey-miryanov

Lib/test/test_ctypes/test_pointers.py

@@ -287,10 +287,16 @@ def test_pointer_set_type_twice(self):
         self.assertIs(t1._type_, c_int)
 
     def test_pointer_set_wrong_type(self):
+        class C(c_int):
+            pass
+
         t1 = POINTER(c_int)
         with self.assertRaisesRegex(TypeError, "pointer type already set"):
             t1.set_type(c_float)
 
+        with self.assertRaisesRegex(TypeError, "cls type already set"):
+            t1.set_type(C)
+
     def test_pointer_not_ctypes_type(self):
         with self.assertRaisesRegex(TypeError, "must have storage info"):
             POINTER(int)