This also means that we need a `tests/__init__.py` file; this file makes
py.test undertand what is our sources directory, and thus allows them to
`import flamenco_worker`. As a result, the test imports from tests/*.py
need to change to relative imports.
I'm guessing the do_db_push() async function execution was starved by
other asyncio tasks, causing Python to remember all the to-be-queued
payloads in memory. By making the function synchronous this doesn't happen.
This is a clone of the Flamenco repository from back in the days when
Server, Manager and Worker shared the same Git repository. This is the
commit where that ended, and they went their separate ways.
