docker run --rm --env-file /path/to/variables -d -p 8000:8000 django_app:test

docker run --rm -d --env-file /path/to/secrets/variables -p 5432:5432
    -v "$PWD/my-postgres.conf":/etc/postgresql/postgresql.conf
    --mount src=/path/to/db/data,dst=/var/lib/postgresql/data,type=bind
    postgres:alpine -c 'config_file=/etc/postgresql/postgresql.conf'

DJANGO_SETTINGS_MODULE=settings.module
PROJECT_KEY=xxyyzzabcdefg
DB_ENGINE=django.db.backends.postgresql
POSTGRES_DB=db_name
POSTGRES_USER=db_user
POSTGRES_PASSWORD=verydifficultpassword
POSTGRES_HOST=localhost # I've also tried to use 0.0.0.0
POSTGRES_PORT=5432

DATABASES = {
    'default': {
        'ENGINE': os.environ.get('DB_ENGINE'),
        'NAME': os.environ.get('POSTGRES_DB'),
        'USER': os.environ.get('POSTGRES_USER'),
        'PASSWORD': os.environ.get('POSTGRES_PASSWORD'),
        'HOST': os.environ.get('POSTGRES_HOST'),
        'PORT': os.environ.get('POSTGRES_PORT')
        }
  }

django.db.utils.OperationalError: could not connect to server: Connection refused
    Is the server running on host "0.0.0.0" and accepting
    TCP/IP connections on port 5432?

FROM python:alpine3.7
COPY --from=installer /app /app
# required for postgres
COPY --from=installer /usr/lib /usr/lib
COPY --from=installer /usr/local/bin /usr/local/bin
COPY --from=installer /usr/local/lib /usr/local/lib
ARG SETTINGS_MODULE
WORKDIR /app
ENTRYPOINT python manage.py migrate &&
           python manage.py test &&
           python manage.py create_default_groups &&
           python manage.py set_screen_permissions &&
           python manage.py create_test_users &&
           python manage.py init_core &&
           python manage.py runserver 0.0.0.0:8000