Use unittest test runner for doctests in test_statistics (pythonGH-10…

…8921)

Lib/test/test_statistics.py

@@ -698,14 +698,6 @@ def test_check_all(self):
                             'missing name "%s" in __all__' % name)
 
 
-class DocTests(unittest.TestCase):
-    @unittest.skipIf(sys.flags.optimize >= 2,
-                     "Docstrings are omitted with -OO and above")
-    def test_doc_tests(self):
-        failed, tried = doctest.testmod(statistics, optionflags=doctest.ELLIPSIS)
-        self.assertGreater(tried, 0)
-        self.assertEqual(failed, 0)
-
 class StatisticsErrorTest(unittest.TestCase):
     def test_has_exception(self):
         errmsg = (
@@ -3145,6 +3137,7 @@ def tearDown(self):
 def load_tests(loader, tests, ignore):
     """Used for doctest/unittest integration."""
     tests.addTests(doctest.DocTestSuite())
+    tests.addTests(doctest.DocTestSuite(statistics))
     return tests