Rewrite celery tasks as decorated functions
Also rename s/i/tests/test_utils.py as s/i/t/utils.py so pytest does not try to execute this file.
related to T1480
Test Plan
there is one test that fails on my machine (with tox),
Metadata.test_compute_metadata_pkginfo (test_metadata.py:670)
Migrated from D980 (view on Phabricator)