Comment 30 for bug 1594740

Proving that the original issue still exists:

peter@mbp> sudo apt install supervisor
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  supervisor-doc
The following NEW packages will be installed:
  supervisor
0 upgraded, 1 newly installed, 0 to remove and 3 not upgraded.
Need to get 252 kB of archives.
After this operation, 1,398 kB of additional disk space will be used.
Get:1 http://nl.archive.ubuntu.com/ubuntu xenial/universe amd64 supervisor all 3.2.0-2 [252 kB]
Fetched 252 kB in 0s (625 kB/s)
Selecting previously unselected package supervisor.
(Reading database ... 241488 files and directories currently installed.)
Preparing to unpack .../supervisor_3.2.0-2_all.deb ...
Unpacking supervisor (3.2.0-2) ...
Processing triggers for systemd (229-4ubuntu16) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up supervisor (3.2.0-2) ...
Processing triggers for systemd (229-4ubuntu16) ...
Processing triggers for ureadahead (0.100.0-19) ...
peter@mbp> ps auxw | grep '[s]upervisor'
peter@mbp>

No output, Supervisor is not running. Now I enable the xenial-proposed archive, opt-out of upgrading my main system from xenial-proposed and selectively install the fixed supervisor package from the proposed archive:

peter@mbp> sudo apt install supervisor/xenial-proposed
Reading package lists... Done
Building dependency tree
Reading state information... Done
Selected version '3.2.0-2ubuntu0.1' (Ubuntu:16.04/xenial-proposed [all]) for 'supervisor'
Suggested packages:
  supervisor-doc
The following packages will be upgraded:
  supervisor
1 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
Need to get 253 kB of archives.
After this operation, 1,024 B of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu xenial-proposed/universe amd64 supervisor all 3.2.0-2ubuntu0.1 [253 kB]
Fetched 253 kB in 1s (242 kB/s)
(Reading database ... 241609 files and directories currently installed.)
Preparing to unpack .../supervisor_3.2.0-2ubuntu0.1_all.deb ...
Unpacking supervisor (3.2.0-2ubuntu0.1) over (3.2.0-2) ...
Processing triggers for systemd (229-4ubuntu16) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up supervisor (3.2.0-2ubuntu0.1) ...
peter@mbp> ps auxw | grep '[s]upervisor'
root 15688 1.8 0.2 59148 18796 ? Ss 21:50 0:00 /usr/bin/python /usr/bin/supervisord -n -c /etc/supervisor/supervisord.conf

As you can see in the 'ps auxw' output the Supervisor daemon is now running.