ref: c37faa91eaa4308b2bb6102562e4ca3bb496abd8
dir: /sys/src/cmd/aux/flashfs/errors.c/
char Edirnotempty[] = "directory not empty on deletion"; char Eexists[] = "file already exists"; char Enonexist[] = "file does not exist"; char Eisdir[] = "is a directory"; char Enotdir[] = "not a directory"; char Eperm[] = "permission denied"; char Erofs[] = "read only filesystem";