Delete TESTFN after the test.
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 03cdfef..193130e 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -54,6 +54,9 @@
 
 class IOTest(unittest.TestCase):
 
+    def tearDown(self):
+        test_support.unlink(test_support.TESTFN)
+
     def write_ops(self, f):
         f.write(b"blah.")
         f.seek(0)