Unfortunately, the EcsRunLauncher doesn't support the local development
instructions becuase the local Docker containers can't use
https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-metadata-endpoint-v4.html
to introspect information about itself. Additionally, we can't use the
AWS SDK to launch local docker containers via the ECS API.
This shouldn't be merged until https://dagster.phacility.com/D8404 lands
and is published to pypi - prior to that, containers will fail to stand up
because the EcsRunLauncher class won't exist yet.