无法安装watir gem

gem install watir

C:DevKit>gem install watir
Building native extensions.  This could take a while...
ERROR:  Error installing watir:
        ERROR: Failed to build gem native extension.

C:/Ruby/bin/ruby.exe extconf.rb
checking for strncpy_s()... no
creating Makefile.....

C:Ruby

ruby dk.rb install

C:/Ruby/lib/ruby/1.8/yaml.rb:133:in `load': syntax error on line 15, col -1: `'
(ArgumentError)
        from C:/Ruby/lib/ruby/1.8/yaml.rb:133:in `load'
        from dk.rb:151:in `review'
        from dk.rb:143:in `open'
        from dk.rb:143:in `review'
        from dk.rb:248:in `send'
        from dk.rb:248:in `run'
        from dk.rb:262