docs: def get_aes_mode(mode):
      """Return pycrypto's AES mode, raise exception if not supported"""
      aes_mode_attr = "MODE_{}".format(mode.upper())
      try:
          aes_mode = getattr(AES, aes_mode_attr)
      except AttributeError:
          raise Exception(
              "Pycrypto/pycryptodome does not seem to support {}. ".format(aes_mode_attr) +
              "If you use pycrypto, you need a version >= 2.7a1 (or a special branch)."
          )
      return aes_mode