itest: add itest logger

In order for the oracle server harness to have a native way of providing
us with logs in the itests we need to set up an itest logger, which is
also initiated during test harness setup.

Author: GeorgeTsagk

itest/log.go

@@ -0,0 +1,24 @@
+package itest
+
+import (
+	"github.com/btcsuite/btclog"
+	"github.com/lightningnetwork/lnd/build"
+)
+
+const Subsystem = "ITST"
+
+// log is a logger that is initialized with no output filters. This means the
+// package will not perform any logging by default until the caller requests it.
+var log btclog.Logger
+
+// The default amount of logging is none.
+func init() {
+	UseLogger(build.NewSubLogger(Subsystem, nil))
+}
+
+// UseLogger uses a specified Logger to output package logging info.
+// This should be used in preference to SetLogWriter if the caller is also
+// using btclog.
+func UseLogger(logger btclog.Logger) {
+	log = logger
+}

itest/test_harness.go

@@ -12,6 +12,7 @@ import (
 	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/rpcclient"
+	"github.com/btcsuite/btclog"
 	"github.com/go-errors/errors"
 	"github.com/lightninglabs/aperture"
 	"github.com/lightninglabs/lndclient"
@@ -207,7 +208,11 @@ func (h *harnessTest) setupLogging() {
 	tap.SetupLoggers(h.logWriter, h.interceptor)
 	aperture.SetupLoggers(h.logWriter, h.interceptor)
 
-	h.logWriter.SetLogLevels(*logLevel)
+	UseLogger(build.NewSubLogger(Subsystem, func(tag string) btclog.Logger {
+		return h.logWriter.GenSubLogger(tag, func() {})
+	}))
+
+	h.logWriter.SetLogLevels("debug")
 }
 
 func (h *harnessTest) newLndClient(