yanglint BUGFIX more output files are forbidden
diff --git a/tools/lint/cmd_print.c b/tools/lint/cmd_print.c
index 2f46c51..a6b815a 100644
--- a/tools/lint/cmd_print.c
+++ b/tools/lint/cmd_print.c
@@ -81,13 +81,11 @@
         switch (opt) {
         case 'o': /* --output */
             if (yo->out) {
-                if (ly_out_filepath(yo->out, optarg) != NULL) {
-                    YLMSG_E("Unable to use output file %s for printing output.\n", optarg);
-                    return 1;
-                }
+                YLMSG_E("Only a single output can be specified.\n");
+                return 1;
             } else {
                 if (ly_out_new_filepath(optarg, &yo->out)) {
-                    YLMSG_E("Unable to use output file %s for printing output.\n", optarg);
+                    YLMSG_E("Unable open output file %s (%s)\n", optarg, strerror(errno));
                     return 1;
                 }
             }