Modernize unittest example
diff --git a/Doc/tutorial/stdlib.rst b/Doc/tutorial/stdlib.rst
index 1343649..f6239d6 100644
--- a/Doc/tutorial/stdlib.rst
+++ b/Doc/tutorial/stdlib.rst
@@ -278,8 +278,10 @@
        def test_average(self):
            self.assertEqual(average([20, 30, 70]), 40.0)
            self.assertEqual(round(average([1, 5, 7]), 1), 4.3)
-           self.assertRaises(ZeroDivisionError, average, [])
-           self.assertRaises(TypeError, average, 20, 30, 70)
+           with self.assertRaises(ZeroDivisionError):
+               average([])
+           with self.assertRaises(TypeError):
+               average(20, 30, 70)
 
    unittest.main() # Calling from the command line invokes all tests