provide more info in case no movie is found

Several users reported an issue with "more than one group found (0)",
and it was unclear to them what it meant. This might help.

couchpotato/core/plugins/scanner/main.py

@@ -329,14 +329,17 @@ class Scanner(Plugin):
 
         del movie_files
 
+        total_found = len(valid_files)
+
         # Make sure only one movie was found if a download ID is provided
-        if download_info and not len(valid_files) == 1:
+        if download_info and total_found == 0:
+            log.info('Download ID provided (%s), but no groups found! Make sure the download contains valid media files (fully extracted).', download_info.get('imdb_id'))
+        elif download_info and total_found > 1:
             log.info('Download ID provided (%s), but more than one group found (%s). Ignoring Download ID...', (download_info.get('imdb_id'), len(valid_files)))
             download_info = None
 
         # Determine file types
         processed_movies = {}
-        total_found = len(valid_files)
         while True and not self.shuttingDown():
             try:
                 identifier, group = valid_files.popitem()