ref: 1dfb1b73ee62bad1b86bda8045a6c0d25717ff83
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";