Error: .ini file does not include supervisorctl section

Adding a blank [supervisorctl] section seems to resolve the issue for me:

$ cat /etc/supervisor/supervisord.conf 
[supervisord]
nodaemon=true

[supervisorctl]

In the supervisor version 3+, I had to add the following in the conf file to make it work:

[inet_http_server]         
port=127.0.0.1:9001

[rpcinterface:supervisor]
supervisor.rpcinterface_factory = supervisor.rpcinterface:make_main_rpcinterface

[supervisorctl]
serverurl=http://127.0.0.1:9001

or you may use unix socket as:

[unix_http_server]
file=/run/supervisord.sock

[supervisorctl]
serverurl=unix:///run/supervisord.sock