Bug#791577: reportbug: trips over obsolete conffiles

[Mechtilde Stehmann]

I want to reopen this bug report.

I tested this last change and it doesn’t work. See also #797922

In the Traceback you see the latest version of line 362 of 
/usr/lib/python2.7/dist-packages/reportbug/utils.py

Kind regards

Mechtilde