Update app.py

app.py

@@ -132,7 +132,7 @@ def request_to_v2(message, cookie, user_id,attachment=None,context=[]):
             attachments = [attachment_response]
             print(f"attachment_response:{attachment_response}")
         else:
-            bots = {"Error: Invalid file format. Please try again."}
+            bots = "Error: Invalid file format. Please try again."
             print(bots)
             context += [bots]
             responses = [(u, b) for u, b in zip(context[::2], context[1::2])]