https://bugzilla.wikimedia.org/show_bug.cgi?id=55246
--- Comment #14 from Kunal Mehta (Legoktm) legoktm.wikipedia@gmail.com --- Aaand http://bugs.python.org/issue10567 is related to that.
In essence: bots running < 2.7 were technically doing the wrong thing, but this did not go noticed as no-one used the interwiki to the tibetan wikipedia, and all bots did the same wrong thing. Now there are bots running 2.7+, from the toolserver, and the bug surfaced.