Why is this a release blocker? If you configure without threads, you get
a few ugly compiler messages, but Python still builds exactly the same
way as without this patch, right?

So if the patch doesn't make it into 2.6, it can still be applied in
2.6.1 (as it is a clear bugfix).

Tentatively lowering priority to normal.

As for reviewing it: indeed, it looks overly complicated (perhaps it
would look nicer in Rietveld). As a last-minute change, I would prefer
something that looks more along the lines of Amaury's fragment (i.e.
trying to avoid changes to the indentation level).