Previously, if you wrote (device "my-label") without (title 'label),
you'd get:
guix system: error: stat: No such file or directory: "my-label"
Now you get a proper error and a hint.
Reported by Pierre-Antoine Rouby.
* guix/scripts/system.scm (check-file-system-availability)[literal]: New
variable. Loop over LITERAL.
* gnu/system/file-systems.scm (%pseudo-file-system-types): New variable.
* guix/ui.scm (display-hint): Make public.