Update deps and use a local caching repo for poetry

.drone.yml

@@ -14,6 +14,7 @@ steps:
       # Install dependencies
       - cp vrobbler.conf.test vrobbler.conf
       - pip install poetry
+      - poetry config repositories.unblink "https://pypi.unbl.ink/pypi/simple"
       - poetry install
       # Start with a fresh database (which is already running as a service from Drone)
       - poetry run pytest --cov-report term:skip-covered --cov=vrobbler tests