def encode_int(cls, obj):
    """Verify the object is an int, and ASCII-encode it.

    :param int obj: An integer to be encoded.
    :raises: :class:`TypeError` if `obj` is not an integer.
    :return: A binary representation of the int `obj` suitable to pass as the `payload` to
             send_exit().
    """
    if not isinstance(obj, int):
      raise TypeError("cannot encode non-integer object in encode_int(): object was {} (type '{}')."
                      .format(obj, type(obj)))
    return str(obj).encode('ascii')