It looks like the html reporter does not handle tests with the outcome retried.

It's quite easy to reproduce:

1. Create a failing test with the mark @pytest.mark.flaky(retries=3, delay=1)
2. Run the test and wait for it to fail so that it is retried
3. Pytest crashes with:

File "/__w/xi/xi/tests/venv/lib/python3.9/site-packages/pytest_html/report_data.py", line 94, in outcomes
  self._outcomes[outcome.lower()]["value"] += 1
KeyError: 'retried'