failure was using snprint where vsnprint was needed.

Reference: /n/sources/patch/applied/factotum-print
Date: Mon Oct 20 12:01:08 CES 2008
Signed-off-by: forsyth@terzarima.net

--- /sys/src/cmd/auth/factotum/util.c	Mon Oct 20 12:00:52 2008
+++ /sys/src/cmd/auth/factotum/util.c	Mon Oct 20 12:00:49 2008
@@ -275,7 +275,7 @@
 		rerrstr(s->err, sizeof(s->err));
 	else {
 		va_start(arg, fmt);
-		snprint(e, sizeof e, fmt, arg);
+		vsnprint(e, sizeof e, fmt, arg);
 		va_end(arg);
 		strecpy(s->err, s->err+sizeof(s->err), e);
 		werrstr(e);