list-models should point out list-controllers command in error message

It would be really nice if the error message formats were the same and included a little bit more information when no model is available.

I have multiple controllers and multiple models. I deleted one of the controllers and its models and when I ran `juju status` I was given a nice error message:

$ juju status
  ERROR no model in focus

  Please use "juju models" to see models available to you.
  You can set current model by running "juju switch"
  or specify any other model on the command line using the "-m" flag.

But when I ran `juju models`:

$ juju models
  error: no controller

  Please either create your own new controller using "juju bootstrap" or
  connect to another controller that you have been given access to using "juju register".

Note how the structure is a little different but also, I have other controllers registered and I simply have to switch to them. It would be nice if this message also included information about `juju controllers` as the previous one had information about `juju models`