Fix unchecked select.poll reference in setUp and tearDown for

platforms that don't have it.

Lib/test/test_telnetlib.py

@@ -169,12 +169,14 @@ def test_telnet(reads=(), cls=TelnetAlike, use_poll=None):
 class ExpectAndReadTestCase(TestCase):
     def setUp(self):
         self.old_select = select.select
-        self.old_poll = select.poll
         select.select = mock_select
+        if hasattr(select, 'poll'):
+            self.old_poll = select.poll
             select.poll = MockPoller
             MockPoller.test_case = self
 
     def tearDown(self):
+        if hasattr(select, 'poll'):
             MockPoller.test_case = None
             select.poll = self.old_poll
         select.select = self.old_select