def make_pkey(key_type=crypto.TYPE_RSA, key_bits=4096):
  """Make a public/private key pair.

  :param int key_type: The key type. For example,
    :class:`OpenSSL.crypto.TYPE_RSA`.
  :param int key_bits: The size of the key in bits.
  :return: A private key.
  :rtype: :class:`OpenSSL.crypto.PKey`

  """
  key = crypto.PKey()
  key.generate_key(key_type, key_bits)
  return key