# File lib/fog/ecloud/collection.rb, line 10
      def check_href!(opts = {})
        unless href
          opts = { :parent => opts } if opts.is_a?(String)
          msg = ":href missing, call with a :href pointing to #{if opts[:message]
                  opts[:message]
                elsif opts[:parent]
                  "the #{opts[:parent]} whos #{self.class.to_s.split('::').last.downcase} you want to enumerate"
                else
                  "the resource"
                end}"
          raise Fog::Errors::Error.new(msg)
        end
      end