Fixed code misc. quality issues (#9649)

- Merge 'isinstance' calls.
- Remove unnecessary dict call outside of comprehension.
- Use 'sys.exit()' calls.

scripts/move_remote_media_to_new_store.py

@@ -51,7 +51,7 @@ def main(src_repo, dest_repo):
         parts = line.split("|")
         if len(parts) != 2:
             print("Unable to parse input line %s" % line, file=sys.stderr)
-            exit(1)
+            sys.exit(1)
 
         move_media(parts[0], parts[1], src_paths, dest_paths)