I had a detector that raised an IOError exception due to a file it was 
trying to open that had the wrong ownership. The apache ssl_error_log 
showed this for the issue I was trying to edit:

Premature end of script headers: roundup.cgi, referer: 
https://tracker.labmed.uw.edu/systems/issue129

The problem was that client.py's Client.inner_main method has an except 
clause for IOError that simply was 'pass' causing no HTTP headers, hence 
the apache error.

I have a fix that works by generating the normal 'An error has occurred' 
message to the user, and an stack trace email to the roundup admin.

I'm not happy about the way it has to get access to the 
send_error_to_admin method. Hopefully you have a better way.