This plugin wants to write to sys.stdout (this is not allowed under mod_wsgi by default; it can be made allowable, but that hides the error). I set sys.stdout to sys.stderr, and now see in /var/log/apache/error_log
[Thu Dec 27 19:28:23 2007] [error] self.billing_reports=set([9, 10, 11, 12, 13, 14, 15, 16, 17])
[Thu Dec 27 19:29:19 2007] [error] self.billing_reports=set([9, 10, 11, 12, 13, 14, 15, 16, 17])
[Thu Dec 27 19:28:23 2007] [error] self.billing_reports=set([9, 10, 11, 12, 13, 14, 15, 16, 17])
[Thu Dec 27 19:29:19 2007] [error] self.billing_reports=set([9, 10, 11, 12, 13, 14, 15, 16, 17])
[Thu Dec 27 19:29:41 2007] [error] self.billing_reports=set([])
[Thu Dec 27 19:29:41 2007] [error] self.billing_reports=set([])
[Thu Dec 27 19:34:25 2007] [error] self.billing_reports=set([])
[Thu Dec 27 19:34:26 2007] [error] self.billing_reports=set([])
The earlier ones are 'working' (reports 10..17), the set([]) ones are the report 9 calls that are failing (as reported in #2334).