LegacyKeyValueFormat warning #1478
Description
docker build . for https://github.com/jupyterhub/repo2docker/blob/067e14a1af960c0979b04b6a65e663bb1943ef08/tests/dockerfile/simple/Dockerfile produces
LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 11)