Give an error if runtime is unavailable when updating
Submitted by Matthias Clasen
Recently, the telegram flatpak was switched to use a kde runtime. Jan updated the RuntimeRepo in his flatpakref to point to the new repository, but for existing users, the update was not installable, since it was requiring a runtime which no configured remote provided.
At the very least, I would expect gnome-software to notice the error, inform the user, and mark the update as uninstallable.