package postgresql-contrib-9.6 9.6.3-0ubuntu0.17.04 failed to install/upgrade: subprocess installed pre-removal script returned error exit status 2

[Ibukunoluwa Dairo]

Crashes

ProblemType: Package
DistroRelease: Ubuntu 17.04
Package: postgresql-contrib-9.6 9.6.3-0ubuntu0.17.04
ProcVersionSignature: Ubuntu 4.10.0-22.24-generic 4.10.15
Uname: Linux 4.10.0-22-generic x86_64
ApportVersion: 2.20.4-0ubuntu4.1
Architecture: amd64
Date: Mon Jun 12 14:42:21 2017
DpkgTerminalLog:
 Removing postgresql-contrib-9.6 (9.6.3-0ubuntu0.17.04) ...
 update-alternatives: error: alternative path /usr/share/postgresql/9.6/man/man1/postmaster.1.gz doesn't exist
 dpkg: error processing package postgresql-contrib-9.6 (--remove):
  subprocess installed pre-removal script returned error exit status 2
ErrorMessage: subprocess installed pre-removal script returned error exit status 2
InstallationDate: Installed on 2017-05-06 (37 days ago)
InstallationMedia: Ubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
RelatedPackageVersions:
 dpkg 1.18.10ubuntu2
 apt 1.4
SourcePackage: postgresql-9.6
Title: package postgresql-contrib-9.6 9.6.3-0ubuntu0.17.04 failed to install/upgrade: subprocess installed pre-removal script returned error exit status 2
UpgradeStatus: No upgrade log present (probably fresh install)

[Christian Ehrhardt  (paelzer)]

Hi,
thank you for your report and your help to make Ubuntu better.

I tried to recreate:
$ apt install postgresql
$ dpkg -S /usr/share/postgresql/9.6/man/man1/postmaster.1.gz
  postgresql-9.6: /usr/share/postgresql/9.6/man/man1/postmaster.1.gz
$ apt remove postgresql

And I see:
Removing postgresql-contrib-9.6 (9.6.3-0ubuntu0.17.04) ...
update-alternatives: warning: forcing reinstallation of alternative /usr/share/postgresql/9.6/man/man1/postmaster.1.gz because link group postmaster.1.gz is broken

So both our cases have that file missing, yet in my repro-case dpkg detects that and removes it correctly.

The file itself is a very old compat name:
update-alternatives: using /usr/share/postgresql/9.6/man/man1/postmaster.1.gz to provide /usr/share/man/man1/postmaster.1.gz (postmaster.1.gz) in auto mode
Quoting from that:
"postmaster is a deprecated alias of postgres."

So in your case something seems to break that - but I can't see from the logs what :-/
Could you report back what the following shows you:
$ dpkg -S /usr/share/postgresql/9.6/man/man1/postmaster.1*
$ ls -laF /usr/share/postgresql/9.6/man/man1/postmaster.1*

Maybe we find some sort of half installed or half removed file that causes this.
Other than that I wanted to ask if you have any sort of third party packages installed that could cause this?

[Launchpad Janitor (janitor)]

[Expired for postgresql-9.6 (Ubuntu) because there has been no activity for 60 days.]