Cannot purge biond glance-common (train)

Try:

sudo apt-get --purge remove glance-common glance-api glance

Does that work?

For diagnostic purposes, what is the output of the commands

uname -a
lsb_release -crid
apt-cache policy glance-common glance-api glance
cat -n /var/lib/dpkg/info/glance-common.postrm
getent passwd glance
getent group glance

I assume the user (or group) glance is not marked as "system" user (or group) which makes the postremove script fail at the command "deluser --system" or delgroup --system"

"I assume the user (or group) glance is not marked as "system" user (or group) which makes the postremove script fail at the command "deluser --system" or delgroup --system" "

@m-hampl This is exactly what I was thinking.

I managed to remove the package and reinstall it but something is still broken.

I have installed the whole server from scratch to see if it's something the can be reproduced on a clean system, and it is reproducible.

output of the commands you gave me:
+ uname -a
Linux controller-1 4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
+ lsb_release -crid
Distributor ID: Ubuntu
Description: Ubuntu 18.04.4 LTS
Release: 18.04
Codename: bionic
+ apt-cache policy glance-common glance-api glance
glance-common:
  Installed: (none)
  Candidate: 2:19.0.3-0ubuntu1~cloud0
  Version table:
     2:19.0.3-0ubuntu1~cloud0 500
        500 http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/train/main amd64 Packages
        100 /var/lib/dpkg/status
     2:16.0.1-0ubuntu1.1 500
        500 http://il.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
     2:16.0.0-0ubuntu1 500
        500 http://il.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
glance-api:
  Installed: (none)
  Candidate: 2:19.0.3-0ubuntu1~cloud0
  Version table:
     2:19.0.3-0ubuntu1~cloud0 500
        500 http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/train/main amd64 Packages
     2:16.0.1-0ubuntu1.1 500
        500 http://il.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
     2:16.0.0-0ubuntu1 500
        500 http://il.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
glance:
  Installed: (none)
  Candidate: 2:19.0.3-0ubuntu1~cloud0
  Version table:
     2:19.0.3-0ubuntu1~cloud0 500
        500 http://ubuntu-cloud.archive.canonical.com/ubuntu bionic-updates/train/main amd64 Packages
     2:16.0.1-0ubuntu1.1 500
        500 http://il.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
     2:16.0.0-0ubuntu1 500
        500 http://il.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
+ cat -n /var/lib/dpkg/info/glance-common.postrm
     1 #!/bin/sh
     2
     3 set -e
     4
     5 case $1 in
     6 purge)
     7 if (which deluser && getent passwd glance) > /dev/null 2>&1; then
     8 deluser --system --quiet --backup-to /var/lib glance
     9 fi
    10 if (which delgroup && getent group glance) > /dev/null 2>&1; then
    11 delgroup --system --quiet glance
    12 fi
    13 ;;
    14 esac
    15
    16
+ getent passwd glance
glance:x:64062:64062::/var/lib/glance:/bin/false
+ getent group glance
glance:x:64062:
+ set +x

To resolve the issue "manually" I tried to run:
deluser --quiet --backup-to /var/lib glance
delgroup --quiet glance

then:
apt purge glance-common glance glance-api

and after this everything runs great.

So the issue is the "--system" in the postrm function/file.

I suggest you report a bug. The uninstall file seems faulty. Hopefully a new one will be made soon to make this smoother