[Nbd] more user-friendly error message

[Milos Jakubicek <xjakub@...541...>]

Hi folks,

we recently had a bug filed against the nbd Fedora package claiming 
about the clarity of the error message which is printed when the nbd 
module is not loaded:

https://bugzilla.redhat.com/show_bug.cgi?id=496751

What about merging a tiny patch I attached?

Regards,
Milos

--- nbd-client.c.orig	2009-05-14 00:27:34.000000000 +0200
+++ nbd-client.c	2009-05-14 00:29:28.000000000 +0200
@@ -232,7 +232,7 @@
 	if (strcmp(argv[0], "-d")==0) {
 		nbd = open(argv[1], O_RDWR);
 		if (nbd < 0)
-			err("Can not open NBD: %m");
+			err("Cannot open NBD: %m\nPlease ensure the 'nbd' module is loaded.");
 		printf("Disconnecting: que, ");
 		if (ioctl(nbd, NBD_CLEAR_QUE)< 0)
 			err("Ioctl failed: %m\n");
@@ -276,7 +276,7 @@
 	nbddev = argv[0];
 	nbd = open(nbddev, O_RDWR);
 	if (nbd < 0)
-	  err("Can not open NBD: %m");
+	  err("Cannot open NBD: %m\nPlease ensure the 'nbd' module is loaded.");
 	++argv; --argc; /* skip device */
 
 	if (argc>3) goto errmsg;