Ok, I reread https://docs.python.org/3/library/sqlite3.html#controlling-transactions several times now. I think it's confusing.

I want explicit transaction handling, but ``isolation_level = None`` turns on "autocommit mode". Unfortunately I don't have suggestions on how to improve the documentation.

For us, ``isolation_level = None`` and the explicit ``begin immediate`` seems to be the correct way and it works with all Python versions, including 3.6.0.

So, I would say this is "not a bug" in Python, but my understanding of the sqlite3 module is flawed. The documentation could be better, but I don't know how to make it better.