def assertNotInLog(self, line, marker=None):
        """Fail if the given (partial) line is in the log.

        The log will be searched from the given marker to the next
        marker. If marker is None, self.lastmarker is used. If the log
        hasn't been marked (using self.markLog), the entire log will be
        searched.
        """
        data = self._read_marked_region(marker)
        for logline in data:
            if line in logline:
                msg = '%r found in log' % line
                self._handleLogError(msg, data, marker, line)
Fail if the given (partial) line is in the log.

        The log will be searched from the given marker to the next
        marker. If marker is None, self.lastmarker is used. If the log
        hasn't been marked (using self.markLog), the entire log will be
        searched.
        
cherrypy/test/logtest.py