Complain if we will do nothing

loki/remux.py

@@ -279,6 +279,10 @@ def lang(media):
     file['lang_vers'] = lang_vers
 
 # Execute
+logger.debug(f"Root: {root}")
+if not root.is_dir():
+  print(f"Invalid root directory: {root}", file=sys.stderr)
+  sys.exit(-1)
 for (parent, dirs, files) in root.walk():
   logger.debug(f"Walking: {parent}")
   media = scan(files)