This reuse the swh.core.db.db_utils postgresql_fact fixture (which inits the db
then truncate tables in between test calls). This makes the tests faster.
without the diff, on my machine:
tox 22.35s user 5.83s system 39% cpu 1:11.02 total
with the diff, on my machine:
tox 13.50s user 2.88s system 78% cpu 20.811 total
We'll see more clearly once D4300 lands (by checking jenkins then).