Variável DB_HOST causa Unknown MySQL server host 'mysql' (-2) | Gitlab CI e Docker: Pipeline de entrega contínua

Ao seguir as instruções do vídeo e setar a variável DB_HOST com o valor 'mysql' o pipeline quebrou apresentando o erro "Unknown MySQL server host 'mysql' (-2)". Segue meu arquivo gilab-ci.yml

image: docker:stable

stages:
- pre-build
- build
- test
- deploy

build-docker:
  services:
  - docker:dind

  before_script:
  - docker info
  - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD

  stage: pre-build
  script:
      - docker build -t minha-imagem .
      - docker tag minha-imagem anderson021285/minha-imagem:latest
      - docker push anderson021285/minha-imagem:latest

build-project:
  image: anderson021285/minha-imagem:latest
  services:
    - docker:dind 
    - mysql:5.7

  variables:
    MYSQL_USER: devops_dev
    MYSQL_PASSWORD: mestre 
    MYSQL_DATABASE: todo_dev 
    MSQL_ROOT_PASSWORD: senha 

    DB_NAME: 'todo_dev'
    DB_USER: 'devops_dev'
    DB_PASSWORD: 'mestre'
    DB_PORT: '3306'
    DB_HOST: 'mysql'
    SECRET_KEY: 'r*5ltfzw-61ksdm41fuul8+hxs$86yo9%k1%k=(!@=-wv4qtyv'

  stage: build
  tags:
    - executor-tarefas
  dependencies:
    - build-docker
  script:
    - python manage.py makemigrations
    - python manage.py migrate

A syout de erro no gitlab é muito grande para colocar aqui, tem como enviar por outro canal ? Acredito que seja algo relacionado a permissão entre os containers, mas não consegui resolver.

Segue parte do log que mostra que devo inserir mais informações para iniciar o banco

*** WARNING: Service runner-8x25xs87-project-21195393-concurrent-0-5397c0b5e9fccd4b-mysql-1 probably didn't start properly.
Health check error:
service "runner-8x25xs87-project-21195393-concurrent-0-5397c0b5e9fccd4b-mysql-1-wait-for-service" timeout
Health check container logs:
Service container logs:
2020-09-22T23:49:09.548512681Z 2020-09-22 23:49:09+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 5.7.31-1debian10 started.
2020-09-22T23:49:10.250485047Z 2020-09-22 23:49:10+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
2020-09-22T23:49:10.305393888Z 2020-09-22 23:49:10+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 5.7.31-1debian10 started.
2020-09-22T23:49:10.913031643Z 2020-09-22 23:49:10+00:00 [ERROR] [Entrypoint]: Database is uninitialized and password option is not specified
2020-09-22T23:49:10.913108520Z     You need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD