Setting up sqlite3 with Python and flask

I’m trying to use Travis CI to test my Python flask backend that uses a simple sqlite3 database.

When trying to initialize the database, I get the following error: sqlite3.OperationalError: unable to open database file. I suspect that I have to setup sqlite3 somehow within Travis since the DB init works fine on my machine.

In the Travis Docs, I only found [this description for sqlite3 with Ruby]. Not sure, how this would work for Python. Adding sqlite or sqlite3 as service in the .travis.yml seems to be forbidden. Adding a config/database.yml as suggested in the docs doesn’t help either.

How do I have to setup sqlite3 with Python within Travis? Or is the error actually coming from something else?