[chef] Help with Chef::CookbookLoader for 0.7.16

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Hi!

I'm trying to develop a application that uses Chef for deploying Software.
Because of that, I need to get all available cookbooks. I found the
CookbookLoader-class but it seems that it doesn't work.
When I try

c_list = Chef::CookbookLoader.new

I can't access any cookbook. Trying to get the apache2 cookbook I get the 
error

/usr/lib/ruby/gems/1.8/gems/chef-0.7.16/lib/chef/cookbook_loader.rb:126:in
`[]': Cannot find a cookbook named apache2; did you forget to add metadata to 
a
cookbook? (http://wiki.opscode.com/display/chef/Metadata) (ArgumentError)

but I have no idea why it isn't working.

Any suggestions?