Return log file of first file handler associated with the (root) logger.
        None if no such handler is found.

def get_logfile(logger=None):
    """ Return log file of first file handler associated with the (root) logger.
        None if no such handler is found.
    """
    logger = logger or logging.getLogger()
    handlers = [i for i in logger.handlers if isinstance(i, logging.FileHandler)]
    return handlers[0].baseFilename if handlers else None