Comment 27 for bug 1768379

To verify that python3-minimal and python3-apt could unpack I had to do the same bit of editing my sources from xenial to bionic to get python3.6-minimal installed, after that the verification succeeded.

bdmurray@clean-xenial-amd64:~$ sudo dpkg --unpack python3-minimal_3.6.5-3ubuntu1_amd64.deb
(Reading database ... 246796 files and directories currently installed.)
Preparing to unpack python3-minimal_3.6.5-3ubuntu1_amd64.deb ...
Unpacking python3-minimal (3.6.5-3ubuntu1) over (3.5.1-3) ...
Processing triggers for man-db (2.7.5-1) ...
bdmurray@clean-xenial-amd64:~$ sudo dpkg --unpack python3-apt_1.6.1_amd64.deb
(Reading database ... 246796 files and directories currently installed.)
Preparing to unpack python3-apt_1.6.1_amd64.deb ...
Unpacking python3-apt (1.6.1) over (1.1.0~beta1ubuntu0.16.04.1) ...