(Merge 3.4) Issue #11259: asynchat.async_chat().set_terminator() now raises a

ValueError if the number of received bytes is negative.

Lib/test/test_asynchat.py

@@ -311,5 +311,13 @@ class TestFifo(unittest.TestCase):
         self.assertEqual(f.pop(), (0, None))
 
 
+class TestNotConnected(unittest.TestCase):
+    def test_disallow_negative_terminator(self):
+        # Issue #11259
+        client = asynchat.async_chat()
+        self.assertRaises(ValueError, client.set_terminator, -1)
+
+
+
 if __name__ == "__main__":
     unittest.main()