dpkg-reconfigure docker.io also does not reproduce the original problem.
Either the problem was present in bionic and fixed in cosmic; or it is a consequence of the debconf frontend being started up in the middle of the release upgrade and having a somehow incoherent filesystem.
Test package noisy-fake-driver from https:/ /launchpad. net/~vorlon/ +archive/ ubuntu/ debconf- tests/+ packages does not reproduce the problem in an upgraded cosmic environment.
dpkg-reconfigure docker.io also does not reproduce the original problem.
Either the problem was present in bionic and fixed in cosmic; or it is a consequence of the debconf frontend being started up in the middle of the release upgrade and having a somehow incoherent filesystem.