lntest: add new wait for conf helper method to ChainNotifier

lntest/harness_assertion.go

@@ -18,6 +18,7 @@ import (
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
+	"github.com/davecgh/go-spew/spew"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/invoicesrpc"
@@ -552,8 +553,10 @@ func (h HarnessTest) WaitForChannelCloseEvent(
 	require.NoError(h, err)
 
 	resp, ok := event.Update.(*lnrpc.CloseStatusUpdate_ChanClose)
-	require.Truef(h, ok, "expected channel close update, instead got %v",
-		event.Update)
+	require.Truef(
+		h, ok, "expected channel close update, instead got %T: %v",
+		event.Update, spew.Sdump(event.Update),
+	)
 
 	txid, err := chainhash.NewHash(resp.ChanClose.ClosingTxid)
 	require.NoErrorf(h, err, "wrong format found in closing txid: %v",