Comment 7 for bug 1615318

During another 14.04->16.04 LTS upgrade:

Setting up daemontools (1:0.76-6ubuntu1) ...
Setting up daemontools-run (1:0.76-6ubuntu1) ...
Adding SV inittab entry...
start: Job is already running: svscan
dpkg: error processing package daemontools-run (--configure):
 subprocess installed post-installation script returned error exit status 1
Setting up dialog (1.3-20160209-1) ...

== DuplicateSignature =================================
package:daemontools-run:1:0.76-6ubuntu1
Setting up daemontools-run (1:0.76-6ubuntu1) ...
Adding SV inittab entry...
start: Job is already running: svscan
dpkg: error processing package daemontools-run (--configure):
 subprocess installed post-installation script returned error exit status 1

== ErrorMessage =================================
subprocess installed post-installation script returned error exit status 1

== Package =================================
daemontools-run 1:0.76-6ubuntu1

== PackageArchitecture =================================
all

== ProblemType =================================
Package

== ProcVersionSignature =================================
Ubuntu 3.13.0-110.157-generic 3.13.11-ckt39

== RelatedPackageVersions =================================
dpkg 1.18.4ubuntu1.1
apt 1.2.19

== SourcePackage =================================
daemontools

== Tags =================================
 xenial

== Title =================================
package daemontools-run 1:0.76-6ubuntu1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

== Uname =================================
Linux 3.13.0-110-generic i686

== UpgradeStatus =================================
Upgraded to xenial on 2017-02-25 (0 days ago)

What would you like to do? Your options are:
  S: Send report (419.6 KB)
  V: View report
  K: Keep report file for sending later or copying to somewhere else
  I: Cancel and ignore future crashes of this program version
  C: Cancel
Please choose (S/V/K/I/C):

Issue still present with the 16.04 package being installed over top of the 14.04 package.

Package dnscache-run was not downloaded during the LTS upgrade process, only daemontools-run.

$ ls -al | grep dnscache-run
$ ls -al | grep daemontools-run
-rw-r--r-- 1 root root 6454 Jan 7 2015 daemontools-run_1%3a0.76-6ubuntu1_all.deb

The "usual" uninstall / IPL / reinstall per #4 again was the work-around.