gunicorn entrypoint throws error using Dockerfile from official documentation

[mxchinegod]

Attempting to deploy the configuration recommended by documentation to enable Alerting & Reports in a Docker environment, the Superset image(s) fail on an entrypoint with a gunicorn command saying not found.

How to reproduce the bug

1. Go to official documentation
2. Create image using aforementioned Dockerfile as instructed (including the .py config)
3. Attempt to use Docker image in a deployment
4. Experience failure at entrypoint command for said image.

Expected results

Docker container to work (all else being equal regarding other container nodes)

Actual results

/usr/bin/docker-entrypoint.sh: line 21: exec: gunicorn --bind 0.0.0.0:8088 --access-logfile - --error-logfile - --workers 5 --worker-class gthread --threads 4 --timeout 200 --limit-request-line 4094 --limit-request-field_size 8190 superset.app: not found

Screenshots

If applicable, add screenshots to help explain your problem.

Environment

(please complete the following information):

• browser type and version:
• superset version: apache/superset:1.0.1
• python version: python --version
• node.js version: node -v
• any feature flags active:

Checklist

Make sure to follow these steps before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if there are any.
• I have reproduced the issue with at least the latest released version of superset.
• I have checked the issue tracker for the same issue and I haven't found one similar.

Additional context

My Dockerfile:

version: '3.6'
services:
  redis:
    image: redis:6.0.9-buster
    restart: on-failure
    volumes:
      - /mnt/zfs-nce-qa/infswmnceunxd/superset/redis:/mnt/zfs-nce-qa/infswmnceunxd/superset/redis
  postgres:
    image: postgres
    restart: on-failure
    environment:
      POSTGRES_DB: superset
      POSTGRES_PASSWORD: superset
      POSTGRES_USER: superset
    volumes:
      - /mnt/zfs-nce-qa/infswmnceunxd/superset/postgres:/mnt/zfs-nce-qa/infswmnceunxd/superset/postgres
  worker:
    image: <internally managed Nexus>/superset:latest
    restart: on-failure
    healthcheck:
      disable: true
    depends_on:
      - superset
      - postgres
      - redis
    command: 
      - 'celery --app=superset.tasks.celery_app:app worker --pool=gevent --concurrency=500'
    volumes:
      - /mnt/zfs-nce-qa/infswmnceunxd/superset/python:/mnt/zfs-nce-qa/infswmnceunxd/superset/python
  beat:
    image: <internally managed Nexus>/superset:latest
    restart: on-failure
    healthcheck:
      disable: true
    depends_on:
      - superset
      - postgres
      - redis
    command: 
      - 'celery --app=superset.tasks.celery_app:app beat --pidfile /tmp/celerybeat.pid --schedule /tmp/celerybeat-schedule'
    volumes:
      - /mnt/zfs-nce-qa/infswmnceunxd/superset/python:/mnt/zfs-nce-qa/infswmnceunxd/superset/python
  superset:
    image: <internally managed Nexus>/superset:latest
    restart: on-failure
    environment:
      - SUPERSET_PORT=8088
    ports:
      - "8088:8088"
    depends_on:
      - postgres
      - redis
    command: 
      - 'gunicorn --bind  0.0.0.0:8088 --access-logfile - --error-logfile - --workers 5 --worker-class gthread --threads 4 --timeout 200 --limit-request-line 4094 --limit-request-field_size 8190 superset.app'
    volumes:
      - /mnt/zfs-nce-qa/infswmnceunxd/superset/python:/mnt/zfs-nce-qa/infswmnceunxd/superset/python
volumes:
  redis:
    external: true
  db:
    external: true

superset_config.py.txt

I have also seen that previous versions used superset.app:create_app(), and newer ones leave the command at superset.app according to #8795

I have tried both on the 1.0.1 and latest registry objects.

[mxchinegod]

Just wanted to add that removing

command: 
      - 'gunicorn --bind  0.0.0.0:8088 --access-logfile - --error-logfile - --workers 5 --worker-class gthread --threads 4 --timeout 200 --limit-request-line 4094 --limit-request-field_size 8190 superset.app:create_app()'

Removed the breaking error and Gunicorn started successfully, so what's going on here?