log level, either from GLib.LogLevelFlags, or a user-defined level
key–value pairs of structured data forming the log message
Optionaluser_data: anyuser data passed to GLib.log_set_writer_func
GLib.LogWriterOutput.HANDLED on success, GLib.LogWriterOutput.UNHANDLED otherwise
Format a structured log message and send it to the syslog daemon. Only fields which are understood by this function are included in the formatted string which is printed.
Log facility will be defined via the SYSLOG_FACILITY field and accepts the following values: "auth", "daemon", and "user". If SYSLOG_FACILITY is not specified, LOG_USER facility will be used.
This is suitable for use as a GLib.LogWriterFunc.
If syslog is not supported, this function is still defined, but will always return GLib.LogWriterOutput.UNHANDLED.