поставил правильный путь к логу

apps/payment/tasks.py

@@ -71,7 +71,7 @@ def transaction_to_roistat(user_id, payment_id, event_name, amount, time, status
     except:
         resp_json = None
 
-    with open("./roistat.log", "a") as text_file:
+    with open("/app/media/roistat.log", "a") as text_file:
 
         if resp.status_code != 200 or not resp_json or not resp_json.get('processed'):
             logger.error('TRANSACTION_TO_ROISTAT for payment # %d, %s RUB: %s' % (