title: Require environment variables to be given to image when run using `-e`
body: <p>I have a container image that requires an environment variable to be set in order to run. But if run with <code>-d</code>, unless the container is monitored, the person running the container won't notice something is missing. Is there a way that <code>docker [container] run</code> checks that an environment variable is given to the container before starting it.</p>