rabbit-mq in Ubuntu 16.04 fails to start without clear message error

Finally I found the detailed error in /var/log/rabbitmq/startup_log which says:

{error_logger,{{2018,10,3},{13,14,18}},“Cookie file /var/lib/rabbitmq/.erlang.cookie must be accessible by owner only”,[]}

I thought it would be better to let rabbitmq create a fresh file, so the solution applied was to remove the erlang cookie file:

rm /var/lib/rabbitmq/.erlang.cookie

After that, restarting rabbitmq makes it work again.