Done. As err gets set on 133, and the func always explicitly returns, it 
actually adds no value.

> In cmd/juju/switch.go:
>
> > @@ -62,7 +124,7 @@ func validEnvironmentName(name string, names []string) bool {
> >  	return false
> >  }
> >
> > -func (c *SwitchCommand) Run(ctx *cmd.Context) error {
> > +func (c *SwitchCommand) Run(ctx *cmd.Context) (err error) {
>
> Please don't do this. It adds noise to the function header and adds 
> very little value.
>
> —
> Reply to this email directly or view it on GitHub 
> <https://github.com/juju/juju/pull/20/files#r13420061>.
>