# File lib/docker/util.rb, line 194
  def extract_id(body)
    body.lines.reverse_each do |line|
      if (id = line.match(/Successfully built ([a-f0-9]+)/)) && !id[1].empty?
        return id[1]
      end
    end
    raise UnexpectedResponseError, "Couldn't find id: #{body}"
  end