Next step after pychecker

[aurora]

A frequent error I encounter

   try:
     ...do something...
   except IOError:
     log('encounter an error %s line %d' % filename)

Here in the string interpolation I should supply (filename,lineno).  
Usually I have a lot of unittesting to catch syntax error in the main  
code. But it is very difficult to run into exception handler, some of  
those are added defensely. Unfortunately those untested exception  
sometimes fails precisely when we need it for diagnosis information.

pychecker sometime give false alarm. The argument of a string  
interpolation  may be a valid tuple. It would be great it we can somehow  
unit test the exception handler (without building an extensive library of  
mock objects).