Docker build is failing because `img` can't be found

[marco-c]

+ apk add --no-cache git img '--repository=http://dl-cdn.alpinelinux.org/alpine/edge/testing' --quiet
ERROR: unsatisfiable constraints:
  img (missing):
    required by: world[img]

[matt-boris]

img was removed in #390. This can be closed.

[marco-c]

And this was fixed a while ago, I don't remember how