title: Ruby Sinatra Hello World Error in `remove_const': constant URI::WFKV_ not defined (NameError)
body: <p>Just trying to get simple http server running and have no clue about ruby</p>
  
  <pre><code>/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.3.5/lib/rack/backports/uri/common_192.rb:53:in `remove_const': constant URI::WFKV_ not defined (NameError)
      from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.3.5/lib/rack/backports/uri/common_192.rb:53:in `&lt;module:URI&gt;'
      from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.3.5/lib/rack/backports/uri/common_192.rb:19:in `&lt;top (required)&gt;'
      from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.3.5/lib/rack/utils.rb:12:in `require'
      from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.3.5/lib/rack/utils.rb:12:in `&lt;top (required)&gt;'
      from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.3.5/lib/rack/request.rb:1:in `require'
      from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.3.5/lib/rack/request.rb:1:in `&lt;top (required)&gt;'
      from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.3.5/lib/rack/showexceptions.rb:3:in `require'
      from /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.3.5/lib/rack/showexceptions.rb:3:in `&lt;top (required)&gt;'
      from /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.3.1/lib/sinatra/showexceptions.rb:1:in `require'
      from /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.3.1/lib/sinatra/showexceptions.rb:1:in `&lt;top (required)&gt;'
      from /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.3.1/lib/sinatra/base.rb:12:in `require'
      from /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.3.1/lib/sinatra/base.rb:12:in `&lt;top (required)&gt;'
      from /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.3.1/lib/sinatra.rb:4:in `require'
      from /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.3.1/lib/sinatra.rb:4:in `&lt;top (required)&gt;'
      from http.rb:1:in `require'
      from http.rb:1:in `&lt;main&gt;'
  </code></pre>
  
  <p>and here is my version of ruby on centos 
  <code>ruby 1.9.1p376 (2009-12-07 revision 26041) [x86_64-linux]</code></p>
  
  <p>any help would be very appreciated</p>