Currently dnspython 2.0.0-1 is stuck in groovy-proposed due to its own autopkgtests failing. After investigating a bit further, it can be seen that the failing (and hanging) tests are ones related to UDP DNS queries using IPv6, which were not tested in the previous dnspython versions. This particularly means the testQueryUDP* tests from tests_query and tests_async (but there's more). The testing suite tries to be as smart as possible and checks for IPv6 connectivity before trying to validate IPv6, but on our infrastructure those checks pass but the UDP tests do not.
This rises the question if the autopkgtest infrastructure (with the network proxy) simply intervenes in the testing, causing those tests to fail, or is this feature broken in Ubuntu. It's worth noting that these autopkgtests are passing fine on Debian.
I have tried preparing an IPv6 setup to check which one is it, but sadly I was unable to get one configured properly - no IPv6 support from my ISP, nor was I able to get IPv6 working via a VPN.
We need someone to check that the failing bits work on a regular setup or not - if yes, we can then simply disable the IPv6 checks in the package and let it migrate.
In case it is the autopkgtest proxy environment causing the failures, I have prepared a debdiff to disable the IPv6 parts of the tests that are failing. But before we proceed, I need to know if it's simply not broken completely on Ubuntu in overall.