Fixed help appearance on empty/unknown commands

Change-Id: I709e05b3c2658da7a8b257e2970f5f4da2e05cf2
Related-PROD: PROD-35610
diff --git a/cfg_checker/nodes.py b/cfg_checker/nodes.py
index 13ab3e7..e028be2 100644
--- a/cfg_checker/nodes.py
+++ b/cfg_checker/nodes.py
@@ -70,7 +70,7 @@
             _valid, _invalid = utils.get_nodes_list(skip_list_file)
             logger_cli.info(
                 "\n# WARNING: Detected invalid entries "
-                "in nodes skip list:\n".format(
+                "in nodes skip list: {}\n".format(
                     "\n".join(_invalid)
                 )
             )