Merge pull request #8 from ros2/fix_fallback_completer_api

fix fallback api without argcomplete

sros2/verb/create_permission.py

@@ -20,7 +20,7 @@ except ImportError:
 try:
     from argcomplete.completers import FilesCompleter
 except ImportError:
-    def FilesCompleter():
+    def FilesCompleter(*, allowednames, directories):
         return None
 
 from sros2.api import create_permission