sudo gem install httpclient

Successfully installed httpclient-2.2.5
1 gem installed
Installing ri documentation for httpclient-2.2.5...


RDoc failure in lib/httpclient.rb at or around line 405 column 16

Before reporting this, could you check that the file
you're documenting compiles cleanly--RDoc is not a
full Ruby parser, and gets confused easily if fed
invalid programs.

The internal error was:

ERROR:  While generating documentation for httpclient-2.2.5
... MESSAGE:   undefined method `name' for #<RubyToken::TkLPAREN:0xb688113c>
... RDOC args: --ri --op /var/lib/gems/1.8/doc/httpclient-2.2.5/ri lib --title httpclient-2.2.5 Documentation --quiet

系统 ubuntu，ruby1.9/rvm 装得。谷歌到一个，但是没搞懂是什么意思 https://github.com/rdoc/rdoc/issues/123