Native subclasses crash with asyncio

[timfel]

I am currently disabling a test in PyO3:
https://github.com/PyO3/pyo3/blob/ee0d6edb6d96e88a9e46d29338ae621f7cd911f2/pytests/tests/test_awaitable.py#L9

When running it we crash with a Java stacktrace and an ArrayIndexOutOfBoundsException