Mark a task as completed

        :param activity: The virtualenv activity name
        :type  activity: ``str``

        :param action: The virtualenv action
        :type  action: :class:`tox.session.Action`

def stop(self, activity, action):
        '''
        Mark a task as completed

        :param activity: The virtualenv activity name
        :type  activity: ``str``

        :param action: The virtualenv action
        :type  action: :class:`tox.session.Action`
        '''
        try:
            self._remove_running_action(activity, action)
        except ValueError:
            retox_log.debug("Could not find action %s in env %s" % (activity, self.name))
        self._mark_action_completed(activity, action)
        self.refresh()