package squid3 3.3.8-1ubuntu6.2 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Dave Strawbridge]

During do-release-upgrade from 12.04 to 14.04.1 LTS
squid.conf had been modified, so I chose to keep it.
As far as I can tell, the rest of the upgrade succeeded.

ProblemType: Package
DistroRelease: Ubuntu 14.04
Package: squid3 3.3.8-1ubuntu6.2
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.5
Architecture: amd64
Date: Sat Nov 29 21:18:23 2014
DuplicateSignature: package:squid3:3.3.8-1ubuntu6.2:subprocess installed post-installation script returned error exit status 1
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2012-04-21 (951 days ago)
InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Beta amd64 (20120421)
SourcePackage: squid3
Title: package squid3 3.3.8-1ubuntu6.2 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: Upgraded to trusty on 2014-11-29 (0 days ago)
mtime.conffile..etc.squid3.squid.conf: 2012-10-18T07:49:05.754698

[Anders Henke (anders-c)]

During upgrade, a message like

---cut
Setting up squid3 (3.3.8-1ubuntu6.2) ...
Creating Squid HTTP proxy 3.x spool directory structure
2014/12/26 14:47:48| aclParseAclLine: ACL 'manager' already exists with different type.
FATAL: Bungled /etc/squid3/squid.conf line 682: acl manager proto cache_object
Squid Cache (Version 3.3.8): Terminated abnormally.
CPU Usage: 0.008 seconds = 0.000 user + 0.008 sys
Maximum Resident Size: 21376 KB
Page faults with physical i/o: 0
dpkg: error processing package squid3 (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 squid3
E: Sub-process /usr/bin/dpkg returned an error code (1)
---cut

shoud've popped up and contains the actual culprit:
the newer version of squid comes with a pre-defined manager-ACL and the line

acl manager proto cache_object

from your /etc/squid3/squid3.conf conflicts with it.

Solution: comment out or remove the line.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.