That sounds good to me.

Just to elaborate on my earlier message, since it might have been too terse:

I think it would be misleading to give in error at:

print >>sys.stderr, "message"

and say:
Did you mean 'print("message")'?

since they're not equivalent. If you can produce the equivalent text in the error message, then that's fine with me:

Did you mean 'print("message", file=sys.stderr)'?