Create a spot instance datafeed subscription for this account.

        :type bucket: str or unicode
        :param bucket: The name of the bucket where spot instance data
                       will be written.  The account issuing this request
                       must have FULL_CONTROL access to the bucket
                       specified in the request.

        :type prefix: str or unicode
        :param prefix: An optional prefix that will be pre-pended to all
                       data files written to the bucket.

        :rtype: :class:`boto.ec2.spotdatafeedsubscription.SpotDatafeedSubscription`
        :return: The datafeed subscription object or None

def create_spot_datafeed_subscription(self, bucket, prefix):
        """
        Create a spot instance datafeed subscription for this account.

        :type bucket: str or unicode
        :param bucket: The name of the bucket where spot instance data
                       will be written.  The account issuing this request
                       must have FULL_CONTROL access to the bucket
                       specified in the request.

        :type prefix: str or unicode
        :param prefix: An optional prefix that will be pre-pended to all
                       data files written to the bucket.

        :rtype: :class:`boto.ec2.spotdatafeedsubscription.SpotDatafeedSubscription`
        :return: The datafeed subscription object or None
        """
        params = {'Bucket' : bucket}
        if prefix:
            params['Prefix'] = prefix
        return self.get_object('CreateSpotDatafeedSubscription',
                               params, SpotDatafeedSubscription, verb='POST')