我想安装 Rails 3.0 Beta,但遇到了似乎是依赖项错误:
$: sudo gem install rack-mount
Successfully installed rack-mount-0.5.1
1 gem installed
Installing ri documentation for rack-mount-0.5.1...
Installing RDoc documentation for rack-mount-0.5.1...
$: sudo gem install rails --prerelease
ERROR: Error installing rails:
actionpack requires rack-mount (~> 0.4.0, runtime)
为什么无法识别机架安装已安装?