title: Ruby Gem package manager failing with Gem::GemNotFoundException
body: <p>I haven't used Ruby for a while on my Mac.  Obviously something has changed in my environment as <code>gem</code> is no longer working as it should.</p>
  
  <p>Some info from my machine, running OSX 10.5.8:</p>
  
  <pre><code>% gem --version
  0.9.0
  
  % gem env
  Rubygems Environment:
    - VERSION: 0.9.0 (0.9.0)
    - INSTALLATION DIRECTORY: /usr/local/lib/ruby/gems/1.8
    - GEM PATH:
       - /usr/local/lib/ruby/gems/1.8
    - REMOTE SOURCES:
       - http://gems.rubyforge.org
  </code></pre>
  
  <p>The error I'm seeing is:</p>
  
  <pre><code>% sudo gem update --system
  Password:
  Updating RubyGems...
  Attempting remote update of rubygems-update
  ERROR:  While executing gem ... (RuntimeError)
      rubygems-update requires builder &gt;= 0
  </code></pre>
  
  <p>Or if I try to install a new gem:</p>
  
  <pre><code>% sudo gem install bossman
  ERROR:  While executing gem ... (Gem::GemNotFoundException)
      Could not find bossman (&gt; 0) in the repository
  </code></pre>
  
  <p>Some people have recommended clearing out the <code>source_cache</code> file, but this didn't help me.  Others recommended:</p>
  
  <pre><code>% gem clean
  Cleaning up installed gems...
  Clean Up Complete
  </code></pre>
  
  <p>But that also doesn't help.</p>
  
  <p>Can someone please help me get <code>gem</code> working again?  Any insight into the reasoning behind this would be helpful.  I know sufficiently little about Ruby and <code>gem</code> to find these error messages cryptic.</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>I tried <a href="https://stackoverflow.com/questions/2273503/ruby-gem-package-manager-failing-with-gemgemnotfoundexception/2273706#2273706">Derick Bailey's suggestion</a>, but without any luck:</p>
  
  <pre><code>% sudo gem install rubygems-update update_rubygems
  Password:
  ERROR:  While executing gem ... (RuntimeError)
      rubygems-update requires builder &gt;= 0
  </code></pre>