Kubuntu Distribution Upgrade tool: self.progressbar of KDECdromProgressAdapter class in DistUpgradeViewKDE.py

as I have a slow internet connection, I have downloaded the alternate CD and executed the cdromupgrade script but it crashes even after I tried to fix the gksu to kdesu that leads me to DistUpgradeViewKDE.py in cdrom/dists/feisty/main/dist-upgrader/binary-all/feisty.tar.gz that contains the following class

class KDECdromProgressAdapter(apt.progress.CdromProgress):
    """ Report the cdrom add progress """
    def __init__(self, parent):
        self.status = parent.window_main.label_status
        self.progress = parent.window_main.progressbar_cache
        self.parent = parent

    def update(self, text, step):
        """ update is called regularly so that the gui can be redrawn """
        if text:
          self.status.setText(text)
 percent = step
        self.progressbar.setProgress(percent)
        KApplication.kApplication().processEvents()

    def askCdromName(self):
        return (False, "")

    def changeCdrom(self):
        return False

I believe in __init__ the 2nd line should be
self.progressbar = parent.window_main.progressbar_cache
as self.progressbar is not defined in the update function.