def write_file(self, what, filename, data):
        """Write `data` to `filename` (if not a dry run) after announcing it

        `what` is used in a log message to identify what is being written
        to the file.
        """
        log.info("writing %s to %s", what, filename)
        if sys.version_info >= (3,):
            data = data.encode("utf-8")
        if not self.dry_run:
            f = open(filename, 'wb')
            f.write(data)
            f.close()