test: introduce get_weight() helper for CTransaction

test/functional/p2p_segwit.py

@@ -4,7 +4,6 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test segwit transactions and blocks on P2P network."""
 from decimal import Decimal
-import math
 import random
 import struct
 import time
@@ -1367,10 +1366,9 @@ class SegWitTest(BitcoinTestFramework):
         raw_tx = self.nodes[0].getrawtransaction(tx3.hash, 1)
         assert_equal(int(raw_tx["hash"], 16), tx3.calc_sha256(True))
         assert_equal(raw_tx["size"], len(tx3.serialize_with_witness()))
-        weight = len(tx3.serialize_with_witness()) + 3 * len(tx3.serialize_without_witness())
-        vsize = math.ceil(weight / 4)
+        vsize = tx3.get_vsize()
         assert_equal(raw_tx["vsize"], vsize)
-        assert_equal(raw_tx["weight"], weight)
+        assert_equal(raw_tx["weight"], tx3.get_weight())
         assert_equal(len(raw_tx["vin"][0]["txinwitness"]), 1)
         assert_equal(raw_tx["vin"][0]["txinwitness"][0], witness_program.hex())
         assert vsize != raw_tx["size"]