# File lib/rhc/helpers.rb, line 244
    def certificate_key(file)
      file && OpenSSL::PKey::RSA.new(IO.read(File.expand_path(file)))
    rescue => e
      debug e
      raise OptionParser::InvalidOption.new(nil, "The RSA key '#{file}' cannot be loaded: #{e.message} (#{e.class})")
    end