fix this test to actually test something (closes #13606)

Thanks Mark Shannon.

Lib/test/test_module.py

@@ -70,9 +70,11 @@ def test_clear_dict_in_ref_cycle(self):
         m = ModuleType("foo")
         m.destroyed = destroyed
         s = """class A:
+    def __init__(self, l):
+        self.l = l
     def __del__(self):
-        destroyed.append(1)
-a = A()"""
+        self.l.append(1)
+a = A(destroyed)"""
         exec(s, m.__dict__)
         del m
         gc_collect()