The newer patch is good.

I found another use of PyAST_FromNode() with NULL flags, and which has 
the same problem:

import parser
s=parser.suite(
     "from __future__ import unicode_literals; print type('')")
eval(s.compile())

But I don't know how to correct this: the CO_FUTURE_UNICODE_LITERALS 
flag is determined during the parse phase (in parser.suite), but this 
value is lost and not passed to s.compile().
Maybe PyST_Object could grow a "st_flags" attribute.