Reverting the Revision: 77368.  I committed Flox's big patch for tests by
mistake. ( It may come in for sure tough)
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 48ffd45..a90dd50 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -381,11 +381,11 @@
             f = None
             try:
                 with self.open(support.TESTFN, "wb", bufsize) as f:
-                    1 // 0
+                    1/0
             except ZeroDivisionError:
                 self.assertEqual(f.closed, True)
             else:
-                self.fail("1 // 0 didn't raise an exception")
+                self.fail("1/0 didn't raise an exception")
 
     # issue 5008
     def test_append_mode_tell(self):