Comment 11 for bug 1024590

It looks like the error is caused by the following bit of code in aptdaemon/gtk3widgets.py:

        try:
            iter = self._download_map[uri]
        except KeyError:
            adj = self.get_vadjustment()

self.get_vadjustment() is returning None, probably because nothing has called set_vadjustment. This might actually be an error in update-manager but I don't see anything having set that in update-manager versions back to Precise.