🔊 Add consistent errors for env vars not set (#200)

{{cookiecutter.project_slug}}/scripts/deploy.sh

@@ -3,14 +3,14 @@
 # Exit in case of error
 set -e
 
-DOMAIN=${DOMAIN} \
-TRAEFIK_TAG=${TRAEFIK_TAG} \
-STACK_NAME=${STACK_NAME} \
-TAG=${TAG} \
+DOMAIN=${DOMAIN?Variable not set} \
+TRAEFIK_TAG=${TRAEFIK_TAG?Variable not set} \
+STACK_NAME=${STACK_NAME?Variable not set} \
+TAG=${TAG?Variable not set} \
 docker-compose \
 -f docker-compose.yml \
 config > docker-stack.yml
 
 docker-auto-labels docker-stack.yml
 
-docker stack deploy -c docker-stack.yml --with-registry-auth "${STACK_NAME}"
+docker stack deploy -c docker-stack.yml --with-registry-auth "${STACK_NAME?Variable not set}"