安装Sass时出错(Ruby 2.5.0.1,MSYS2 20161025.0.0)

我试图安装Sass。我已安装 红宝石 和 MSYS2 在此之前 Chocolatey :

choco install ruby
choco install msys2

看起来它们安装得很好。 ruby -v 结果如下:

ruby 2.5.0p0 (2017-12-25 revision 61468) [x64-mingw32]

当我想跑的时候 gem install sass 我收到以下错误消息:

ERROR:  Error installing sass:
        The last version of ffi (< 2, >= 0.5.0) to support your Ruby & RubyGems was 1.9.18. Try installing it with `gem install ffi -v 1.9.18` and then running the current command again
        ffi requires Ruby version < 2.5, >= 2.0. The current ruby version is 2.5.0.

好的,所以我试着跑 gem install ffi -v 1.9.18 .

我收到了这个错误消息:

ERROR:  Error installing ffi:
        The last version of ffi (= 1.9.18) to support your Ruby & RubyGems was 1.9.18. Try installing it with `gem install ffi -v 1.9.18`
        ffi requires Ruby version < 2.5, >= 2.0. The current ruby version is 2.5.0.

我试图用正确的安装程序重新安装Ruby,重新启动了计算机,但出现了相同的错误。

如何使Sass安装?