test: Use int.to_bytes over struct packing

This is done in prepration for the scripted diff, which can not deal
with those lines.

test/functional/p2p_invalid_messages.py

@@ -5,7 +5,6 @@
 """Test node responses to invalid network messages."""
 
 import random
-import struct
 import time
 
 from test_framework.messages import (
@@ -233,7 +232,7 @@ class InvalidMessagesTest(BitcoinTestFramework):
                 '208d'))     # port
 
     def test_addrv2_unrecognized_network(self):
-        now_hex = struct.pack('<I', int(time.time())).hex()
+        now_hex = int(time.time()).to_bytes(4, "little").hex()
         self.test_addrv2('unrecognized network',
             [
                 'received: addrv2 (25 bytes)',

test/functional/test_framework/script.py

@@ -800,13 +800,13 @@ def BIP341_sha_prevouts(txTo):
     return sha256(b"".join(i.prevout.serialize() for i in txTo.vin))
 
 def BIP341_sha_amounts(spent_utxos):
-    return sha256(b"".join(struct.pack("<q", u.nValue) for u in spent_utxos))
+    return sha256(b"".join(u.nValue.to_bytes(8, "little", signed=True) for u in spent_utxos))
 
 def BIP341_sha_scriptpubkeys(spent_utxos):
     return sha256(b"".join(ser_string(u.scriptPubKey) for u in spent_utxos))
 
 def BIP341_sha_sequences(txTo):
-    return sha256(b"".join(struct.pack("<I", i.nSequence) for i in txTo.vin))
+    return sha256(b"".join(i.nSequence.to_bytes(4, "little") for i in txTo.vin))
 
 def BIP341_sha_outputs(txTo):
     return sha256(b"".join(o.serialize() for o in txTo.vout))

test/functional/wallet_balance.py

@@ -4,7 +4,6 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test the wallet balance RPC methods."""
 from decimal import Decimal
-import struct
 
 from test_framework.address import ADDRESS_BCRT1_UNSPENDABLE as ADDRESS_WATCHONLY
 from test_framework.blocktools import COINBASE_MATURITY
@@ -266,8 +265,8 @@ class WalletTest(BitcoinTestFramework):
         tx_orig = self.nodes[0].gettransaction(txid)['hex']
         # Increase fee by 1 coin
         tx_replace = tx_orig.replace(
-            struct.pack("<q", 99 * 10**8).hex(),
-            struct.pack("<q", 98 * 10**8).hex(),
+            (99 * 10**8).to_bytes(8, "little", signed=True).hex(),
+            (98 * 10**8).to_bytes(8, "little", signed=True).hex(),
         )
         tx_replace = self.nodes[0].signrawtransactionwithwallet(tx_replace)['hex']
         # Total balance is given by the sum of outputs of the tx