Deprecation warning in python tests

[hlinnaka]

=============================== warnings summary ===============================
test_runner/fixtures/zenith_fixtures.py:331
  /home/circleci/project/test_runner/fixtures/zenith_fixtures.py:331: DeprecationWarning: invalid escape sequence \w
    for match in re.finditer('-c(\w*)=(\w*)', options):

-- Docs: https://docs.pytest.org/en/stable/warnings.html
==================================== PASSES ====================================

Not urgent, but would be nice to silence that.

[hlinnaka]

We might want to switch to psycopg3 at some point (currently using psycopg2). It includes async support (https://www.psycopg.org/psycopg3/docs/advanced/async.html#async), so we could switch to using that instead of th 'asyncpg' driver. This warning is coming from glue code that translates between the slightly different syntax for setting server options between the drivers; switching to psycopg3 for both sync and async code would allow getting rid of it.