The time diff between 2.7.3 and 2.7.6 is a year and a half, and lib2to3 got a bunch of fixed merge in during that period. I peeked at the CPython logs, and there's a number of changes so this bug may very well have been plugged.

I guess we should be recommending the latest Python 2.7 possible, since it's very difficult for us to work around lib2to3 bugs in yapf - we're basically limited to whatever it can parse. Some things can be monkey-patched, but core parsing bugs are challenging.