Expirable bug list contains private bugs

I assume this is a high issue since we want to release this feature.

The tail of the error:

    * Module zope.tales.tales, line 696, in evaluate
      return expression(self)
      /srv/edge.launchpad.net/edge/launchpad/lib/canonical/launchpad/templates/bugs-listing-table-without-navlinks.pt
      Line 31, Column 10
      Expression: <PathExpr standard:u'bugtask/image:icon'>
         - Names:
            {'args': (),
             'context': <canonical.launchpad.browser.bugtask.BugListingBatchNavigator object at 0x6663650>,
             'default': <object object at 0x2af1e1e471f0>,
             'loop': {},
             'nothing': None,
             'options': {},
             'repeat': {},
             'request': <canonical.launchpad.webapp.servers.BugsBrowserRequest instance URL=https://bugs.edge.launchpad.net/ubuntu/+expirable-bugs>,
             'template': <zope.app.pagetemplate.viewpagetemplatefile.ViewPageTemplateFile object at 0x2af1ea3f6b90>,
             'usage': <zope.pagetemplate.pagetemplate.TemplateUsage object at 0x6f744d0>,
             'view': <zope.app.pagetemplate.simpleviewclass.SimpleViewClass from /srv/edge.launchpad.net/edge/launchpad/lib/canonical/launchpad/templates/bugs-listing-table-without-navlinks.pt object at 0x6f74550>,
             'views': <zope.app.pagetemplate.viewpagetemplatefile.ViewMapper object at 0x6f74510>}
    * Module zope.tales.expressions, line 205, in __call__
      return self._eval(econtext)
    * Module zope.tales.expressions, line 192, in _eval
      ob = self._subexprs[-1](econtext)
    * Module zope.tales.expressions, line 124, in _eval
      ob = self._traverser(ob, element, econtext)
    * Module zope.app.pagetemplate.engine, line 72, in trustedZopeTraverser
      request=getattr(econtext, 'request', None))
    * Module zope.app.traversing.adapters, line 124, in traverse
      curr = traversePathElement(curr, name, path, request=request)
    * Module zope.app.traversing.adapters, line 177, in traversePathElement
      return traversable.traverse(nm, further_path)
    * Module canonical.launchpad.webapp.tales, line 545, in traverse
      return getattr(self, name)()
    * Module canonical.launchpad.webapp.tales, line 558, in icon
      if self._context.importance:
    * Module canonical.lp, line 180, in __get__
      return getattr(getattr(inst, self.contextvar), self.name)

Unauthorized: (<BugTask at 0x2aaaaaf08f10>, 'importance', 'launchpad.View')

This was fixed quite a while ago. I think this is a duplicate of some other bug report, but I can't find it.