在Mac OSX(Lion)上为ruby安装libyaml

我收到此错误消息:

"It seems your ruby installation is missing psych (for YAML output).
To eliminate this warning, please install libyaml and reinstall your ruby."

我尝试输入以下命令:rvm pkg install libyaml

I have tried entering this command: rvm pkg install libyaml

我收到此错误消息:

"Fetching yaml-0.1.4.tar.gz to /Users/luke/.rvm/archives
Extracting yaml-0.1.4.tar.gz to /Users/luke/.rvm/src
Error running 'tar xmzf /Users/luke/.rvm/archives/yaml-0.1.4.tar.gz -C
/Users/luke/.rvm/src ', 
   please read /Users/luke/.rvm/log/yaml/extract.log
Configuring yaml in /Users/luke/.rvm/src/yaml-0.1.4.
Error running ' ./configure --prefix="/Users/luke/.rvm/usr"  ', 
   please read /Users/luke/.rvm/log/yaml/configure.log
Compiling yaml in /Users/luke/.rvm/src/yaml-0.1.4.
Error running 'make ', please read /Users/luke/.rvm/log/yaml/make.log

Database file /Users/luke/.rvm/config/packages does not exist."

有人知道我在做什么错吗?谢谢！

Does anyone know what I am doing wrong? Thanks!