title: Error: blog.Comment: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'
body: <pre><code>mysite-virtualenv) 10:43 ~/django-blog (master)$ ./manage.py migrate
  System check identified some issues:
  WARNINGS:
  blog.Comment: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
          HINT: Configure the DEFAULT_AUTO_FIELD setting or the BlogConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'dja
  ngo.db.models.BigAutoField'.
  blog.Post: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
          HINT: Configure the DEFAULT_AUTO_FIELD setting or the BlogConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'dja
  ngo.db.models.BigAutoField'.
  users.Profile: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
          HINT: Configure the DEFAULT_AUTO_FIELD setting or the UsersConfig.default_auto_field attribute to point to a subclass of AutoField, e.g. 'dj
  ango.db.models.BigAutoField'.
  </code></pre>
  <p>Operations to perform:
  Apply all migrations: admin, auth, blog, contenttypes, sessions, users
  Running migrations:
  No migrations to apply.</p>