> it's different than python3 (for no good reason?)
Python 3 has new style classes which were always different.

> main concern here is ease in portability  
We've long stated that there should never be dependency on the exact wording of an error message.  We're allowed to change that.

> For instance it was consistent in 2.7.1
To the extent we care about this, it is more important to be consistent with later releases than earlier releases.

Since I don't see any evidence that there is a real world problem, I would like to see this left alone.  At this point, in Python 2.7's life we need to have a strong aversion to any changes at all.  Not only has that ship sailed, its voyage is almost over.