Unhandled unauthorized error when showing git repository index

[Adam Collard]

When attempting to access the index of a git repository that I do not have access to, Launchpad raises an Unauthorized exception, but nothing handles this and it leaks out to the top.

OOPS-c80712c71a756dbfdb40f9e8611c083a is an example of this.

Traceback (most recent call last):
  Module zope.publisher.publish, line 129, in publish
    obj = request.traverse(obj)
  Module zope.publisher.browser, line 561, in traverse
    ob, add_steps = publication.getDefaultTraversal(self, ob)
  Module lp.services.webapp.publication, line 228, in getDefaultTraversal
    return superclass.getDefaultTraversal(self, request, ob)
  Module zope.app.publication.browser, line 36, in getDefaultTraversal
    return ob.browserDefault(request)
Unauthorized: (<zope.browserpage.metaconfigure.SimpleViewClass from /srv/launchpad.net/production/launchpad-rev-c597c3229eb023b1e626162d5947141bf7befb13/lib/lp/code/browser/../templates/gitrepository-index.pt object at 0x7f0088017510>, 'browserDefault', 'launchpad.View')

Example URL being: https://code.launchpad.net/%7Ecloudware/livecd-rootfs/+git/cpc_packaging.extra-mwhudson/+index