Error: Another program is already listening on a port that one of our HTTP servers is configured to use.  Shut this program down first before starting supervisord.

*http://serverfault.com/questions/114477/supervisor-http-server-port-issue

sudo unlink /tmp/supervisor.sock

sudo unlink /var/run/supervisor.sock

This .sock file is defined in /etc/supervisord.conf's [unix_http_server]'s file config value (default is /tmp/supervisor.sock or /var/run/supervisor.sock).

Hope this helps someone in the future.