I'm making this a release blocker for 2.7.2 because I want to ensure that the change is deliberate and appropriate.  This is triggered by a bug report in Ubuntu where the change in behavior was noticed:

https://bugs.launchpad.net/nova/+bug/791221/+index

I have two problems with the change that I'd like to describe.  First is the NEWS file entry:

- Correct lookup of __dir__ on objects. Among other things, this causes errors
  besides AttributeError found on lookup to be propagated.

This isn't associated with a tracker issue, so it's hard to know why this change was made, or whether there was any discussion of its impact.

Second, is this change appropriate for a maintenance release?  What problem does it fix and is that worth breaking existing packages for it?

I'll attach a simple test program.  Run this under 2.7.1 and it works, run it under 2.7.2rc1 and you get a TypeError.