Convert a decimal octet into an integer.

        Args:
            octet_str: A string, the number to parse.

        Returns:
            The octet as an integer.

        Raises:
            ValueError: if the octet isn't strictly a decimal from [0..255].

def _parse_octet(self, octet_str):
        """Convert a decimal octet into an integer.

        Args:
            octet_str: A string, the number to parse.

        Returns:
            The octet as an integer.

        Raises:
            ValueError: if the octet isn't strictly a decimal from [0..255].

        """
        # Whitelist the characters, since int() allows a lot of bizarre stuff.
        if not self._DECIMAL_DIGITS.issuperset(octet_str):
            raise ValueError
        octet_int = int(octet_str, 10)
        # Disallow leading zeroes, because no clear standard exists on
        # whether these should be interpreted as decimal or octal.
        if octet_int > 255 or (octet_str[0] == '0' and len(octet_str) > 1):
            raise ValueError
        return octet_int