More on why location is nil. In CookbookSource#cached_and_location
https://github.com/RiotGames/berkshelf/blob/2-0-stable/lib/berkshelf/cookbook_source.rb#L135-137

it calls from_path which returns nil right away because we don't specify a path.

Then it calls from_default and since options doesn't have any location keys in it, location is set to nil
https://github.com/RiotGames/berkshelf/blob/2-0-stable/lib/berkshelf/cookbook_source.rb#L246