[qa] Switch to py3

qa/rpc-tests/test_framework/bignum.py

@@ -1,16 +1,15 @@
-#
+#!/usr/bin/env python3
 #
 # bignum.py
 #
 # This file is copied from python-bitcoinlib.
 #
-# Distributed under the MIT/X11 software license, see the accompanying
+# Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 #
 
 """Bignum routines"""
 
-from __future__ import absolute_import, division, print_function, unicode_literals
 
 import struct