Method unmocked_pull

src/tests/containerizer/provisioner_docker_tests.cpp:325–333

          const Option<Secret>&));

  Future<slave::docker::Image> unmocked_pull(
      const spec::ImageReference& reference,
      const string& directory,
      const string& backend,
      const Option<Secret>& config)
  {
    // TODO(gilbert): Allow return Image to be overridden.
    return slave::docker::Image();
  }
};