Comment 1 for bug 2018932

With help from SEG, we found out that doing `juju config prometheus2 rules-update-ssh-key=@private_ssh_key_file` worked, where the following did not work in my scenario:

`juju config prometheus rules-update-ssh-key="$(cat <private_ssh_key_file>)"`
`juju config prometheus rules-update-ssh-key="<pasted contents of the file>"

This is believed to possibly be related to the way the key was generated (probably PuTTY).