When running a Pipelines build, Pipelines will have to re-pull private Docker images on every single step that it runs. If a single pull ends up failing on a multi-step Pipelines build, the entire build will fail (unless the step that failed is re-run manually).
This feature request is to make it so that Pipelines will temporarily cache private build images on multi-step Pipelines builds or parallel sets, until the build is over, so that it can reuse it during that time on subsequent steps.