Message 168611 - Python tracker

OK, I tracked down the original reason for the behavioural change: #2051

The important aspect in that patch is preserving the *read* permissions from the .py file so we don't accidentally expose data to other users.

Kevin's patch seems like a good approach for restoring compatibility in 2.7 and 3.2

In 3.3, it appears that #2051 has regressed, since no test was added to confirm the correct behaviour and importlib appears to behave more like 2.5.