Comment 5 for bug 1826870

I installed the upgrades, and ran the script in the bug description and see if it got fixed.

xenial python3-apt (1.1.0~beta1ubuntu0.16.04.4) verified - note that the one in -updates is fine too, it only broke for the previous upload in proposed.
bionic python3-apt (1.6.4) verified
cosmic python3-apt (1.7.1) verified

Full testing script for inside a lxd container:

while ! grep cloud-init /etc/apt/sources.list; do
 sleep 1
done
while ! ping -c1 google.com; do
 sleep 1
done
echo "deb http://archive.ubuntu.com/ubuntu $(lsb_release -cs)-proposed main" >> /etc/apt/sources.list
apt update
python3 - << EOF
#!/usr/bin/env python
import apt
import subprocess

cache = apt.Cache()
pkg = cache["hello"]
pkg.mark_install()
cache.commit()
subprocess.check_call(["apt", "remove", "--yes", "hello"])
EOF
apt install python3-apt
python3 - << EOF
#!/usr/bin/env python
import apt
import subprocess

cache = apt.Cache()
pkg = cache["hello"]
pkg.mark_install()
cache.commit()
subprocess.check_call(["apt", "remove", "--yes", "hello"])
EOF

Run like this:

( i=cosmic; lxc launch -e ubuntu:$i test-$i && lxc exec test-$i -- bash -x - < ~/a.sh ; lxc stop test-$i )