logging cleanup failure prevents session start

[quozl]

Logging cleanup creates a directory and moves previous logs into it. This requires available disk space.

When disk space is insufficient, or disk is read-only, or some other I/O error occurs, the sugar-session terminates. On systems that only exist to run sugar-session, the X server is repeatedly restarted. Here is an example from Sugar 0.84 with a full disk:

Traceback (most recent call last):
  File "/usr/bin/sugar-session", line 185, in <module>
    main()
  File "/usr/bin/sugar-session", line 141, in main
    cleanup_logs()
  File "/usr/bin/sugar-session", line 80, in cleanup_logs
    os.mkdir(backup_dir)
OSError: [Errno 28] No queda espacio en el dispositivo: '/home/olpc/.sugar/default/logs/1265854382'

(This example from  dev.laptop.org #9623)

[quozl]

patch for review

[quozl]

This patch not tested.

|testcase|

Fill disk or change ownership of .sugar/default/logs to prevent write by user, then start session. Expected result: session will start. Current result: session fails to start, stderr of sugar-session process shows an IOError exception.

[tomeu]

Pushed, thanks!

 http://git.sugarlabs.org/projects/sugar/repos/mainline/commits/4cde4818