💚 change postgres container

.circleci/config.yml

@@ -13,9 +13,9 @@ jobs: # A basic unit of work in a run
           PIPENV_VENV_IN_PROJECT: true
           DATABASE_URL: postgresql://root@localhost/circle_test?sslmode=disable
       # CircleCI PostgreSQL images available at: https://hub.docker.com/r/circleci/postgres/
-      - image: circleci/postgres:9.6.2
+      - image: circleci/postgres:9.6.9-alpine
         auth:
-          username: mydockerhub-user
+          username: $DOCKERHUB_USERNAME
           password: $DOCKERHUB_PASSWORD  # context / project UI env-var reference
         environment: # environment variables for the Postgres container.
           POSTGRES_USER: root