Give a better message from 'zpool get' when an invalid pool name is p…

…rovided

Signed-off-by: Paul Dagnelie <pcd@delphix.com>

cmd/zpool/zpool_main.c

@@ -10752,9 +10752,9 @@ zpool_do_get(int argc, char **argv)
 		}
 	} else {
 		/*
-		 * The first arg isn't a pool name,
+		 * The first arg isn't the name of a valid pool.
 		 */
-		fprintf(stderr, gettext("missing pool name.\n"));
+		fprintf(stderr, gettext("%s: no such pool.\n"), argv[0]);
 		fprintf(stderr, "\n");
 		usage(B_FALSE);
 		return (1);