title: rubygems 1.3.6 installation fails
body: <p>I have installed ruby 1.9.3 from sources and downloaded rubygems 1.3.6 also source.
  looking at the manual I untarred the tarball and typed <code>ruby setup.rb</code>
  This is what I get as output:</p>
  
  <pre><code>/usr/local/lib/ruby/1.9.1/rubygems.rb:206:in `try_activate': undefined method 
  `find_by_path' for Gem::Specification:Class (NoMethodError)
          from /usr/local/lib/ruby/1.9.1/rubygems/custom_require.rb:59:in `rescue in require'
          from /usr/local/lib/ruby/1.9.1/rubygems/custom_require.rb:35:in `require'
          from /root/rubygems-1.3.6/lib/rubygems/config_file.rb:50:in `&lt;class:ConfigFile&gt;'
          from /root/rubygems-1.3.6/lib/rubygems/config_file.rb:28:in `&lt;top (required)&gt;'
          from /usr/local/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
          from /usr/local/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
          from /root/rubygems-1.3.6/lib/rubygems/gem_runner.rb:8:in `&lt;top (required)&gt;'
          from /usr/local/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
          from /usr/local/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
          from setup.rb:25:in `&lt;main&gt;'
  </code></pre>
  
  <p>This is done on CentOS 5</p>