Warn when the persistence is getting full
People are using Tails on tiny devices with no much disk space. Filling up the persistence while working can lead to weird behaviour of Icedove for example (crashing, etc.). We should warn people when their persistence is getting full.
How is this handled by GNOME? See https://search.disconnect.me/image?l=aHR0cHM6Ly9lbmNyeXB0ZWQtdGJuMC5nc3RhdGljLmNvbS9pbWFnZXM/cT10Ym46QU5kOUdjUjdDMVE4ZkVvMHlyRnhBcGQwWUFscDBFRmhScVc2WXV0bjNNTU81RldWampXRnZuMTBPUQ==.
How could we do that?