discourse/db/fixtures/502_staff_category.rb

unless Rails.env.test?
  staff = Category.where(id: SiteSetting.staff_category_id).first
  if staff and !staff.group_ids.include?(Group[:staff].id)

    # Add permissions and a description to the Staff category.

    staff.group_names = ['staff']
    unless staff.save
      puts staff.errors.full_messages
      raise "Failed to set permissions on the Staff category!"
    end

    creator = PostCreator.new(Discourse.system_user,
      raw: I18n.t('staff_category_description'),
      title: I18n.t('category.topic_prefix', category: staff.name),
      category: staff.name,
      archetype: Archetype.default
    )
    post = creator.create

    unless post && post.id
      puts post.errors.full_messages if post
      puts creator.errors.inspect
      raise "Failed to create description for Staff category!"
    end

    staff.topic_id = post.topic.id
    unless staff.save
      puts staff.errors.full_messages
      puts "Failed to set the Staff category description topic!"
    end

    # Reset topic count because we don't count the description topic
    Category.exec_sql "UPDATE categories SET topic_count = 0 WHERE id = #{staff.id}"
  end
end