feat(python): add conftest.py

[jsstevenson]

Motivated by two things

• the "noisy logs" thing really is annoying in a lot of our stuff and it'd be nice to have the code there to handle it. Easy to delete where it's really unnecessary
• I wanted to add a set of tests to the FastAPI branch I'm working on, but the template doesn't currently include any tests by default, so I wanted to have a little bit of a skeleton there.

[korikuzma]

Makes sense to me!