for sack in self.pkgSack.sacks.values():
            sack.added = {}
            sack.excludes = {}

        self.pkgSack.excludes = {}

        # We need to reset the yum object
        self.pkgSack = None

        # Setup the sack with just src arch
        self.doSackSetup(archlist=['src'])

I have this code snippit in pungi in order to reset the yum object to use the
src arch list instead of whatever arch it was using for this run.  The error
happens at the 'self.pkgSack = None' line.