Comment 3 for bug 615064

This oops was caused calling len(distroseries.packackings) where packagings is a storm query that builds several objects (packaging, productseries, distroseries, product) because most cases where a packaging object wanted is to get the other objects.

But, and this is the insight into this issue: The callsite only wants the count, and this is the only callsite for distroseries.packagings. All the other callsites were recently updated to use specialised methods that wrap the newer _all_packagings cached property.

Remove distroseries.packagings
Add distroseries.packaging_count, it aly be as simple as:
    return len(self._all_packagings)