added a second parameter to evaluate model

app.py

@@ -492,7 +492,7 @@ def update_leaderboard(username, zip_file):
         updated_leaderboard = evaluate_model(username, python_script)
 
         if updated_leaderboard == None:
-            return None
+            return "An error occured while evaluting the model", None
 
     except Exception as e:
         print("Error in eval mode:", str(e))