Mysql2::Error: Access denied for user 'myapp'@'%' to database 'myapp_development': CREATE DATABASE myapp_development DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci
...
Couldn't create database for {"adapter"=>"mysql2", "pool"=>5, "encoding"=>"utf8", "host"=>"db", "username"=>"myapp", "password"=>"secret", "database"=>"myapp_test"}

db:
  image: mysql:latest
  ports:
    - "13306:3306"
  environment:
    MYSQL_USER: myapp
    MYSQL_PASSWORD: secret
    MYSQL_ROOT_PASSWORD: supersecret
web:
  build: .
  command: bundle exec rails s -p 3000 -b '0.0.0.0'
  environment:
    MYSQL_USER: myapp
    MYSQL_PASSWORD: secret
  volumes:
    - .:/myapp
  ports:
    - "3000:3000"
  links:
    - db