Cannot drop postgres test db

Describe the bug
finalizer() fails with

E   asyncpg.exceptions.ObjectInUseError: database "test_db" is being accessed by other users

E   DETAIL:  There is 1 other session using the database.

To Reproduce

@pytest.fixture(scope="session")
def event_loop():
    policy = asyncio.get_event_loop_policy()
    loop = policy.new_event_loop()
    yield loop
    loop.close()


@pytest.fixture(scope="session", autouse=True)
def initialize_tests(request, event_loop):
    initializer(models, db_url=test_db_url)
    request.addfinalizer(finalizer)

Expected behavior
I expect the test db to be dropped as finalizer is calling connections.close_all() before trying to delete the db

Start by tracing the finalizer and connections.close_all() referenced in the report, then reproduce the session-scoped pytest fixture with the PostgreSQL test database. Done means the finalizer can drop test_db without asyncpg.exceptions.ObjectInUseError or another session remaining.