sanitize usernames

app.py

@@ -90,7 +90,8 @@ def push_results_to_hub(user_answers, token: gr.OAuthToken | None):
             "grade": grade,
         }
     )
-    new_ds.push_to_hub(repo_id=repo_id, split=user_info["name"])
+    sanitized_name = user_info["name"].replace("-", "000")
+    new_ds.push_to_hub(repo_id=repo_id, split=sanitized_name)
     return f"Your responses have been submitted to the Hub! Final grade: {grade:.1%}"