These checks need to sudo certain varnish scripts to be able to get status and metrics data.
To ensure sensu can run these commands, add the following to
/etc/sudoers.d/sensu-varnish or wherever you
manage your sudo lists;
# Assuming that your varnish scripts are located in /usr/bin; sensu ALL=(ALL) NOPASSWD: /usr/bin/varnishadm, /usr/bin/varnishstat