I assume that this is not an issue with the model definition itself, but elsewhere. However I just experienced it when configuring a docker agent that uses an image from a private registry. In this case the corporate proxy settings (which are configured in .docker/config.json) and which are usually passed by the docker daemon to the container (via the HTTP(S)_PROXY/NO_PROXY environment variables) are missing from the container. If I switch to a DockerHub image (e.g. ubuntu:16.04), the proxy settings are present in the container.
This is more or less the same issue as
JENKINS-52724, but manifested when using a docker agent and not when building a docker image.