安装Sass时出错(Ruby2.5.0.1,MSYS220161025.0.0)

我试着安装Sass.我之前安装了Ruby和MSYS2,这是所有与Chocolatey的最新产品:

choco install ruby
choco install msys2

看似他们已正确安装.ruby -v结果是:

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

当我尝试运行时gem install sass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,所以我试图跑gem install ffi -v 1.9.18.

我收到此错误消息:

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.

我尝试使用适当的安装程序重新安装Ruby,重新启动计算机,但出现相同的错误.

如何让Sass安装？