Comment 5 for bug 2009191

Hi Paul, I think I remember. The function itself is idempotent, the issue is that by storing (caching) the guessed default release in self.default_release, this `if` will be affected, and change the pinning:

https://salsa.debian.org/ci-team/autopkgtest/-/blob/b4fb54e2a44bbf375d23e34837f377a402c981b2/lib/adt_testbed.py#L401

This only happens at the second test (and later tests), because while running the very first test _get_default_release() was never executed yet, so self.default_release is None and the code under the `if` I pointed to doesn't execute.