Comment 5 for bug 782273

I extracted a script (attached) to experiment with. It contains a
function that's based on ArchiveView.repository_usage, but with some
changes around the quota calculations (authorized_size can be None,
which cannot be used for arithmetic in this version of reality).

The LOSAs sprinting this week so Julian ran this on dogfood, but the
performance was *terrible*. Queries were taking multiple minutes to
complete. It looked almost as though they were just hanging, but
Julian reckoned it was thrashing the disk.

This needs further investigation, and probably with a lot of help from
the LOSAs, so I'm putting this back on the pile until next week when
the LOSAs are fully available once again.