Fix crash in python 3, due to difference in comprenhension list.

theano/gof/cc.py

@@ -345,7 +345,7 @@ def get_c_extract(r, name, sub):
         # check_broadcast is just an hack to easily remove just the
         # broadcast check on the old GPU back-end. THis check isn't
         # done in the new GPU back-end or on the CPU.
-        if hasattr(c.op, 'check_broadcast'):
+        if hasattr(r.clients[-1][0].op, 'check_broadcast'):
             try:
                 c_extract = r.type.c_extract(
                     name, sub, True,