Use @shared_task decorator instead of binding to specific celery app

swh/deposit/loader/tasks.py

-# Copyright (C) 2015-2018  The Software Heritage developers
+# 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 as app
+from celery import shared_task
 
 from swh.deposit.loader.loader import DepositLoader
 from swh.deposit.loader.checker import DepositChecker
 
 
-@app.task(name=__name__ + '.LoadDepositArchiveTsk')
+@shared_task(name=__name__ + '.LoadDepositArchiveTsk')
 def load_deposit_archive(archive_url, deposit_meta_url, deposit_update_url):
     """Deposit archive loading task described by the following steps:
 
@@ -27,7 +27,7 @@ def load_deposit_archive(archive_url, deposit_meta_url, deposit_update_url):
         deposit_update_url=deposit_update_url)
 
 
-@app.task(name=__name__ + '.ChecksDepositTsk')
+@shared_task(name=__name__ + '.ChecksDepositTsk')
 def check_deposit(deposit_check_url):
     """Check a deposit's status