Skip os.sendfile() test if threading module is not available.
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 59a2d63..4965786 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -1352,6 +1352,7 @@
         raise
 
 
+@unittest.skipUnless(threading is not None, "test needs threading module")
 @unittest.skipUnless(hasattr(os, 'sendfile'), "test needs os.sendfile()")
 class TestSendfile(unittest.TestCase):