资产管道不会导入'application.scss'

Question

我正在尝试在我的Rails应用as explained here上设置gem bootstrap-sass。我已将application.css文件重命名为application.scss。以下是文件的内容：

  /*
   * This is a manifest file that'll be compiled into application.css, which will include all the files
   * listed below.
   *
   * Any CSS and SCSS file within this directory, lib/assets/stylesheets, vendor/assets/stylesheets,
   * or any plugin's vendor/assets/stylesheets directory can be referenced here using a relative path.
   *
   * You're free to add application-wide styles to this file and they'll appear at the bottom of the
   * compiled file so the styles you add here take precedence over styles defined in any other CSS/SCSS
   * files in this directory. Styles in this file should be added after the last require_* statement.
   * It is generally better to create a new file per style scope.
   */
   @import "bootstrap-sprockets";
   @import "bootstrap";

但是当在CSS中编译这个文件时，Asset Pipelien不会导入任何内容并输出一个CSS文件，其内容与SASS相同。

我错过了什么？