Auto merge of #3090 - bitcartel:3084_log_expired_txid, r=bitcartel

Closes #3084.  Log txid when removing expired transactions from mempool.

qa/rpc-tests/mempool_tx_expiry.py

@@ -17,7 +17,7 @@ from decimal import Decimal
 class MempoolTxExpiryTest(BitcoinTestFramework):
 
     def setup_nodes(self):
-        return start_nodes(4, self.options.tmpdir, [["-nuparams=5ba81b19:205", "-txexpirydelta=4"]] * 4)
+        return start_nodes(4, self.options.tmpdir, [["-nuparams=5ba81b19:205", "-txexpirydelta=4", "-debug=mempool"]] * 4)
 
     # Test before, at, and after expiry block
     # TODO: Test case of dependent txs in reorgs

src/txmempool.cpp

@@ -271,6 +271,7 @@ void CTxMemPool::removeExpired(unsigned int nBlockHeight)
     for (const CTransaction& tx : transactionsToRemove) {
         list<CTransaction> removed;
         remove(tx, removed, true);
+        LogPrint("mempool", "Removing expired txid: %s\n", tx.GetHash().ToString());
     }
 }