Incomplete abstract class no longer logs an error

We have this test in aiohttp:

def test_testcase_no_app(
    testdir: pytest.Testdir, loop: asyncio.AbstractEventLoop
) -> None:
    testdir.makepyfile(
        """
        from aiohttp.test_utils import AioHTTPTestCase


        class InvalidTestCase(AioHTTPTestCase):
            def test_noop(self) -> None:
                pass
        """
    )
    result = testdir.runpytest()
    result.stdout.fnmatch_lines(["*TypeError*"])

This has started failing sometime after 8.1.1.

The log seems to successfully run, rather than erroring.

Output from the test:

FAILED tests/test_test_utils.py::test_testcase_no_app - Failed: nomatch: '*TypeError*'
    and: '============================= test session starts =============================='
    and: 'platform darwin -- Python 3.11.9, pytest-8.4.1, pluggy-1.6.0'
    and: 'codspeed: 3.2.0 (disabled, mode: walltime, timer_resolution: 41.7ns)'
    and: 'rootdir: /private/var/folders/y6/nj790rtn62lfktb1sh__79hc0000gn/T/pytest-of-runner/pytest-0/popen-gw1/test_testcase_no_app0'
    and: 'plugins: xdist-3.7.0, cov-6.2.1, mock-3.14.1, codspeed-3.2.0'
    and: 'collected 0 items'
    and: ''
    and: '============================ no tests ran in 0.01s ============================='
remains unmatched: '*TypeError*'

Start with tests/test_test_utils.py and test_testcase_no_app, then inspect the testdir.runpytest entry point and the generated InvalidTestCase using AioHTTPTestCase. Reproduce the failure and trace why pytest collects zero tests without logging TypeError. Done means the test again observes the expected TypeError output.