Trace HTTP responses even in the case of errors

This closes long standing issues #297 and #553.

CONTRIBUTORS

@@ -77,6 +77,7 @@ Naoya Tsutsumi [@tutuming](https://github.com/tutuming)
 Nicholas Wolff [@nwolff](https://github.com/nwolff)
 Nick K [@utrack](https://github.com/utrack)
 Nick Whyte [@nickw444](https://github.com/nickw444)
+Nicolae Vartolomei [@nvartolomei](https://github.com/nvartolomei)
 Orne Brocaar [@brocaar](https://github.com/brocaar)
 Pete C [@peteclark-ft](https://github.com/peteclark-ft)
 Radoslaw Wesolowski [r--w](https://github.com/r--w)

client.go

@@ -22,7 +22,7 @@ import (
 
 const (
 	// Version is the current version of Elastic.
-	Version = "5.0.41"
+	Version = "5.0.42"
 
 	// DefaultURL is the default endpoint of Elasticsearch on the local machine.
 	// It is used e.g. when initializing a new Client without a specific URL.

client_test.go

@@ -973,6 +973,22 @@ func TestPerformRequestWithLoggerAndTracer(t *testing.T) {
 		t.Errorf("expected tracer output; got: %q", tgot)
 	}
 }
+func TestPerformRequestWithTracerOnError(t *testing.T) {
+	var tw bytes.Buffer
+	tout := log.New(&tw, "TRACER ", log.LstdFlags)
+
+	client, err := NewClient(SetTraceLog(tout), SetSniff(false))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	client.PerformRequest(context.TODO(), "GET", "/no-such-index", nil, nil)
+
+	tgot := tw.String()
+	if tgot == "" {
+		t.Errorf("expected tracer output; got: %q", tgot)
+	}
+}
 
 type customLogger struct {
 	out bytes.Buffer