If there is no image locally `docker-compose --resolve-image-digests`
will try and get the digest from the repository.
Fixes https://github.com/docker/compose/issues/5818
Signed-off-by: Djordje Lukic <djordje.lukic@docker.com>
`tests/__init__.py` already has a try/except statement to use mock from
the standard library when possible. Take advantage of it like other
tests already do.
Signed-off-by: Carl George <carl@george.computer>