Benjamin, the 2to3 parse tree straddles the 2.x Grammar and 3.x Grammar
(it's its own thing) which is why fixup_parse_tree is there.  From the
docstring:
  one-line classes don't get a suite in the parse tree so we add one to
normalize the tree
The 2to3 parser is very line oriented - only the try/except logic uses
blocks (I think).

There haven't been any objection so I've assigned this to myself and
I'll check it in and close it soonish.