After reading that question I realise I need to install
sudo apt-get install supervisor tells me:
E: Unable to locate package supervisor
sudo apt-cache search supervisor gives nothing.
Also when I look at other questions it seems that it is installed by default in Ubuntu 16.04.
I am using Ubuntu 16.04 LTS.
Why can't I find this package? How can I install it?
I also looked at install recommendation on official doc of supervisor but I would prefer to use the distribution package solution.