Update app.py

app.py

@@ -150,7 +150,7 @@ def call_main(purpose, task, history, directory, action_input):
             else:
                 return action_name, action_input, history, task
         else:
-            history += "observation: my last command caused an ERROR, I need to check the commands syntax, or use a different command\n"
+            history += "observation: the following command did not produce any useful output: '{}', I need to check the commands syntax, or use a different command\n".format(line)
             
             #return action_name, action_input, history, task
             #assert False, "unknown action: {}".format(line)