title: strange bundler error: tar_input.rb:49:in `initialize': not in gzip format (Zlib::GzipFile::Error) on bundle pack
body: <p>i am getting a strange bundler error when running</p>
  
  <pre><code>bundle pack
  </code></pre>
  
  <p>with bundler 0.9.12 </p>
  
  <p>any ideas? (see pastie for a better formatted code: <a href="http://pastie.org/881328" rel="nofollow noreferrer">http://pastie.org/881328</a> )</p>
  
  <pre><code>/opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_input.rb:49:in `initialize': not in gzip format (Zlib::GzipFile::Error)
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_input.rb:49:in `new'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_input.rb:49:in `initialize'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_reader.rb:63:in `each'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_reader.rb:54:in `loop'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_reader.rb:54:in `each'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_input.rb:32:in `initialize'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_input.rb:17:in `new'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package/tar_input.rb:17:in `open'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/package.rb:55:in `open'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/format.rb:63:in `from_io'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/format.rb:51:in `from_file_by_path'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/format.rb:50:in `open'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/site_ruby/1.8/rubygems/format.rb:50:in `from_file_by_path'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/source.rb:115:in `specs'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/source.rb:114:in `each'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/source.rb:114:in `specs'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/index.rb:32:in `from_cached_specs'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/index.rb:23:in `application_cached_gems'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/index.rb:15:in `cached_gems'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/index.rb:5:in `build'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/index.rb:14:in `cached_gems'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/environment.rb:15:in `index'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/index.rb:5:in `build'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/environment.rb:13:in `index'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/runtime.rb:86:in `specs'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/runtime.rb:130:in `details'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/runtime.rb:119:in `write_yml_lock'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/runtime.rb:65:in `lock'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/cli.rb:89:in `lock'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/cli.rb:131:in `package'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/vendor/thor/task.rb:33:in `send'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/vendor/thor/task.rb:33:in `run'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/vendor/thor/invocation.rb:109
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/vendor/thor/invocation.rb:116:in `call'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/vendor/thor/invocation.rb:116:in `invoke'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/vendor/thor.rb:137:in `start'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/vendor/thor/base.rb:378:in `start'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/lib/bundler/vendor/thor.rb:124:in `start'
    from /opt/ruby-enterprise-1.8.7-2010.01/lib/ruby/gems/1.8/gems/bundler-0.9.12/bin/bundle:11
    from /opt/REE/bin/bundle:19:in `load'
    from /opt/REE/bin/bundle:19
  </code></pre>