What is wrong with this code snippet for generating an HTML report?

What is wrong with this code snippet for generating an HTML report?

import unittest
from htmltestrunner import HTMLTestRunner

class MyTests(unittest.TestCase):
    def test_example(self):
        self.assertEqual(1, 1)

suite = unittest.TestLoader().loadTestsFromTestCase(MyTests)
runner = HTMLTestRunner(output=123)
runner.run(suite)