change two "r"s to " %r"s; add some missing ": %r"s.
visible in /sys/log/auth when keyfs starts up:

cpu Aug  1 01:13:26 keyfs starting warnings: 42edd9a6 42ec881f
warning: can't open upas/expire:r

Reference: /n/sources/patch/applied/auth-warning
Date: Mon Aug  1 10:22:20 CES 2005

--- /sys/src/cmd/auth/warning.c	Mon Aug  1 10:20:59 2005
+++ /sys/src/cmd/auth/warning.c	Mon Aug  1 10:20:57 2005
@@ -266,7 +266,7 @@
 	execl("/bin/upas/send", "send", "-r", rcvr, nil);
 
 	/* just in case */
-	fprint(2, "warning can't exec send\n");
+	fprint(2, "warning can't exec send: %r\n");
 	exits("exec send");
 
 	return 0;		/* for compiler */
@@ -295,13 +295,13 @@
 
 	fd = open(file, OREAD);
 	if(fd < 0){
-		complain("can't open %s:r", file);
+		complain("can't open %s: %r", file);
 		return 0;
 	}
 	n = read(fd, buf, sizeof(buf)-1);
 	close(fd);
 	if(n < 0){
-		complain("can't read %s:r", file);
+		complain("can't read %s: %r", file);
 		return 0;
 	}
 	buf[n] = 0;
@@ -315,7 +315,7 @@
 
 	fd = open(file, OWRITE);
 	if(fd < 0){
-		complain("can't open %s", file);
+		complain("can't open %s: %r", file);
 		return;
 	}
 	fprint(fd, "%ld", num);