Writes a line to a log file
    
    Arguments:
        namespace {str} -- namespace of document
        document {dict} -- document to write to the logs

def write_log_file(namespace, document):
    """Writes a line to a log file
    
    Arguments:
        namespace {str} -- namespace of document
        document {dict} -- document to write to the logs
    """
    log_timestamp = asctime(gmtime(document[TS]))
    with open("{}{}.{}.log".format(LOG_DIR, namespace, DAY_STRING), "a") as f:
        log_string = dumps({
            "datetime": log_timestamp.upper(),
            "namespace": namespace,
            "log": document[LOG_KEY]
        })
        f.write("{}\n".format(log_string))