bpo-20092. Use __index__ in constructors of int, float and complex. (GH-13108)

diff --git a/Lib/test/test_index.py b/Lib/test/test_index.py
index a2ac321..cbdc56c 100644
--- a/Lib/test/test_index.py
+++ b/Lib/test/test_index.py
@@ -60,7 +60,7 @@
         # subclasses.  See issue #17576.
         class MyInt(int):
             def __index__(self):
-                return int(self) + 1
+                return int(str(self)) + 1
 
         my_int = MyInt(7)
         direct_index = my_int.__index__()