temBoard 9 can't be run in background

[pgiraud]

Important changes have been made in commit 7328892.

As opposed to what is mentioned in the changelog, it seems impossible to run the agent (I didn't try with the ui) with nohup.

With the following steps:

• configuring temBoard to write logs in a file,
• executing nohup temboard-agent & in a terminal,
• closing the terminal.

the agent terminates with the following message: "INFO: syncio: Parent process exited. Exiting. ppid=xxxxx" .

In my opinion, it's wrong to rely on os.getppid() in https://github.com/dalibo/temboard/blob/master/ui/temboardui/toolkit/syncio.py#L52 to verify if parent process is still running. As far as I understand, we want the child processes (scheduler, worker pool) to check if the main process running temboard is still running. But it seems wrong to search for parent process beyond temboard itself.