If log-delete gets an unexpected exception while deleting logs, it will be logged to /var/log/beaker/server-debug.log but not printed to stdout or stderr, and the exit status will still be 0. That means if something is failing (for example bug 853848) it is very likely the admin will never notice.
The logging of errors and continuing of deletion is by design. We can have thousands of files to delete and I don't think we would want errors with some of them stopping us from deleting the rest. However a more obvious (read 'correct') place for the logs is in order.
The script already tries to send its logs to stderr, line 36 has: log_to_stream(sys.stderr) but something must be going wrong with that.
On Gerrit: http://gerrit.beaker-project.org/1317
Beaker 0.9.4 has been released.