fixes id/pid usage depending on usecase

pgpubsub/listen.py

@@ -212,8 +212,8 @@ def process(self):
             ).first()
         )
         if notification is None:
-            logger.info(f'Could not obtain a lock on notification '
-                        f'{self.notification.id}\n')
+            logger.info(f'Could not obtain a lock on notification pid='
+                        f'{self.notification.pid}\n')
         else:
             logger.info(f'Obtained lock on {notification}')
             self.notification = notification
@@ -230,16 +230,17 @@ def validate(self):
     def process(self):
         logger.info(
             f'Processing notification for {self.channel_cls.name()}')
+        notification_id = int(self.notification.payload)
         notification = (
             Notification.objects.select_for_update(
                 skip_locked=True).filter(
-                    Q(id=int(self.notification.payload)) & get_extra_filter(),
+                    Q(id=notification_id) & get_extra_filter(),
                     channel=self.notification.channel,
             ).first()
         )
         if notification is None:
-            logger.info(f'Could not obtain a lock on notification '
-                        f'{self.notification.id}\n')
+            logger.info(f'Could not obtain a lock on notification id='
+                        f'{notification_id}\n')
         else:
             logger.info(f'Obtained lock on {notification}')
             self.notification = notification