diff --git a/swh/scheduler/task.py b/swh/scheduler/task.py
index ca65742..d2c9cf0 100644
--- a/swh/scheduler/task.py
+++ b/swh/scheduler/task.py
@@ -1,96 +1,97 @@
 # Copyright (C) 2015-2019 The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 from celery import current_app
 import celery.app.task
 from celery.utils.log import get_task_logger
 
 from swh.core.statsd import Statsd
 
 
 class SWHTask(celery.app.task.Task):
     """a schedulable task (abstract class)
 
     Current implementation is based on Celery. See
     http://docs.celeryproject.org/en/latest/reference/celery.app.task.html for
     how to use tasks once instantiated
 
     """
 
     _statsd = None
     _log = None
 
     @property
     def statsd(self):
         if self._statsd:
             return self._statsd
         worker_name = current_app.conf.get('worker_name')
         if worker_name:
             self._statsd = Statsd(constant_tags={
                 'task': self.name,
                 'worker': worker_name,
             })
             return self._statsd
         else:
             return Statsd(constant_tags={
                 'task': self.name,
                 'worker': 'unknown worker',
             })
 
     def __call__(self, *args, **kwargs):
         self.statsd.increment('swh_task_called_count')
         with self.statsd.timed('swh_task_duration_seconds'):
             return super().__call__(*args, **kwargs)
 
     def on_failure(self, exc, task_id, args, kwargs, einfo):
         self.statsd.increment('swh_task_failure_count')
-        self.send_event('task-result-exception')
 
     def on_success(self, retval, task_id, args, kwargs):
         self.statsd.increment('swh_task_success_count')
+        # this is a swh specific event. Used to attach the retval to the
+        # task_run
         self.send_event('task-result', result=retval)
 
     @property
     def log(self):
         if self._log is None:
             self._log = get_task_logger(self.name)
         return self._log
 
     def run(self, *args, **kwargs):
         self.log.debug('%s: args=%s, kwargs=%s', self.name, args, kwargs)
         ret = super().run(*args, **kwargs)
         self.log.debug('%s: OK => %s', self.name, ret)
         return ret
 
 
 class Task(SWHTask):
     """a schedulable task (abstract class)
 
     DEPRECATED! Please use SWHTask as base for decorated functions instead.
 
     Sub-classes must implement the run_task() method.
 
     Current implementation is based on Celery. See
     http://docs.celeryproject.org/en/latest/reference/celery.app.task.html for
     how to use tasks once instantiated
 
     """
 
     abstract = True
 
     def run(self, *args, **kwargs):
         """This method is called by the celery worker when a task is received.
 
         Should not be overridden as we need our special events to be sent for
         the reccurrent scheduler. Override run_task instead."""
         return self.run_task(*args, **kwargs)
 
     def run_task(self, *args, **kwargs):
         """Perform the task.
 
         Must return a json-serializable value as it is passed back to the task
         scheduler using a celery event.
         """
         raise NotImplementedError('tasks must implement the run_task() method')