adduser: Only one or two names allowed.

[davidthewatson]

I'm running draft on macos 10.14.6:

&version.Version{SemVer:"v0.16.0", GitCommit:"5433afea1421810ae9d828631d8651de913b347a", GitTreeState:"dirty"}

I've done:

draft init
draft create
draft up

I get:

building docker image: FAIL
Step 15/50 : RUN adduser --shell /bin/bash --disabled-password --gecos "" ${USER}
 ---> Running in 562a7200aae8
adduser: Only one or two names allowed.
2019/10/25 17:29:14 error while building: The command '/bin/sh -c adduser --shell /bin/bash --disabled-password --gecos "" ${USER}' returned a non-zero code: 1

My source code is:

https://github.com/opencv/cvat

[bjornmagnusson]

Tested this with similar environment.
Issue is that the ARG USER is blank by default when buidling the image (same when using docker build . directly..).
Check image-build-args in https://github.com/Azure/draft/blob/master/docs/reference/dep-006.md for defining build-args for the image building phase in draft