We’ve been modifying /etc/default/docker so that the daemon grabs the “–insecure-registry” option since our test environment requires it, but starting yesterday (or about that), this no longer seems to be propagated to the service.
Apparently the new version uses /etc/docker/daemon.json to configure the daemon.
Adding an example of how I fixed configuring insecure registries in our before_script section of .travis.yml in case other people encounter the same issue: