Use asottile/add-trailing-comma
diff --git a/pre_commit_hooks/check_added_large_files.py b/pre_commit_hooks/check_added_large_files.py
index 8d5f4c4..193b910 100644
--- a/pre_commit_hooks/check_added_large_files.py
+++ b/pre_commit_hooks/check_added_large_files.py
@@ -51,7 +51,7 @@
     parser = argparse.ArgumentParser()
     parser.add_argument(
         'filenames', nargs='*',
-        help='Filenames pre-commit believes are changed.'
+        help='Filenames pre-commit believes are changed.',
     )
     parser.add_argument(
         '--maxkb', type=int, default=500,