Ported usage of deprecated optparse module to argparse module

test/functional/wallet_txn_doublespend.py

@@ -19,8 +19,8 @@ class TxnMallTest(BitcoinTestFramework):
         self.num_nodes = 4
 
     def add_options(self, parser):
-        parser.add_option("--mineblock", dest="mine_block", default=False, action="store_true",
-                          help="Test double-spend of 1-confirmed transaction")
+        parser.add_argument("--mineblock", dest="mine_block", default=False, action="store_true",
+                            help="Test double-spend of 1-confirmed transaction")
 
     def setup_network(self):
         # Start with split network: