Currently the Cirrus CI seems to fail for some reason. No idea why, but maybe invalidating the Docker image cache fixes it?
The failure is:
Failed to start an instance! Failed to pull null image! Repository does not exist or may require authentication.
Container errored with 'ImagePullBackOff: Back-off pulling image "gcr.io/cirrus-ci-community/bitcoin/bitcoin/ci/test_imagefile:b3e086572130d8954f84bb90778d02e2cfbb6dc624c01e2f74ee17335a9c453e"'