PUID typo and error constant fix

Signed-off-by: glindsell <gl@seldon.io>

executor/api/grpc/server_test.go

@@ -20,11 +20,11 @@ func TestAddPuid(t *testing.T) {
 
 func TestExistingPuid(t *testing.T) {
 	g := NewGomegaWithT(t)
-	guid := "1"
+	puid := "1"
 
-	ctx := metadata.NewIncomingContext(context.TODO(), metadata.New(map[string]string{payload.SeldonPUIDHeader: guid}))
+	ctx := metadata.NewIncomingContext(context.TODO(), metadata.New(map[string]string{payload.SeldonPUIDHeader: puid}))
 	meta := CollectMetadata(ctx)
 
 	g.Expect(meta.Get(payload.SeldonPUIDHeader)).NotTo(BeNil())
-	g.Expect(meta.Get(payload.SeldonPUIDHeader)[0]).To(Equal(guid))
+	g.Expect(meta.Get(payload.SeldonPUIDHeader)[0]).To(Equal(puid))
 }

executor/predictor/predictor_process.go

@@ -14,6 +14,8 @@ import (
 	v1 "github.com/seldonio/seldon-core/operator/apis/machinelearning.seldon.io/v1"
 )
 
+const NilPUIDError = "context value for Seldon PUID Header is nil"
+
 type PredictorProcess struct {
 	Ctx       context.Context
 	Client    client.SeldonApiClient
@@ -270,7 +272,7 @@ func (p *PredictorProcess) getPUIDHeader() (string, error) {
 	if puid, ok := p.Ctx.Value(payload.SeldonPUIDHeader).(string); ok {
 		return puid, nil
 	}
-	return "", fmt.Errorf("context value Seldon PUID Header is nil: interface to string conversion failed")
+	return "", fmt.Errorf(NilPUIDError)
 }
 
 func (p *PredictorProcess) Predict(node *v1.PredictiveUnit, msg payload.SeldonPayload) (payload.SeldonPayload, error) {

executor/predictor/predictor_process_test.go

@@ -472,5 +472,5 @@ func TestPredictNilPUIDError(t *testing.T) {
 	graph := &v1.PredictiveUnit{}
 	_, err := createPredictorProcessWithoutPUIDInContext(t).Predict(graph, createPredictPayload(g))
 	g.Expect(err).NotTo(BeNil())
-	g.Expect(err.Error()).Should(Equal("context value Seldon PUID Header is nil: interface to string conversion failed"))
+	g.Expect(err.Error()).Should(Equal(NilPUIDError))
 }