Actually run all the validations.

        Returns:
            list(str): Error messages from the validators.

def _call_validators(self):
        """Actually run all the validations.

        Returns:
            list(str): Error messages from the validators.
        """
        msg = []
        msg.extend(self._validate_keyfile())
        msg.extend(self._validate_dns_zone())
        msg.extend(self._validate_retries())
        msg.extend(self._validate_project())
        return msg