The FixRaise in fix_raise can't fix the py2 code into 2/3 compatible when exception followed by a traceback.

[bulbyang]

The py2 code is here

import sys

traceback = sys.exc_info()[2]

raise ValueError, "wrong value", traceback

The code generated by futurize is here

import sys

traceback = sys.exc_info()[2]

raise ValueError("wrong value").with_traceback(traceback)

The second one is only legal on python3.
I think that it is reasonable to fix the exception with traceback by use the function future.utils.raise_()