What prompted me to do these changes is that "Backward compatibility" 
section for 2.1 and earlier. How long are we going to keep this? According 
to svn, no commit has been made on the 2.1 branch since 2003. Is it safe 
to assume no unittest change is ever going to be backported to 2.1?

Then, while I was in it, I made other changes:

 - dict.has_key(key) --> key in dict
 - raise Exception, args --> raise Exception(args)
 - try..except KeyboardInterrupt: raise except: do_stuff() --> try..except 
Exception: do_stuff()
 - __metaclass__ = type --> all classes are now object subclasses

I'm not sure about the last one. Are those 2 equivalent? Is there a reason 
to keep is as "__metaclass__ = type"?

regrtest passed for me.