Return user friendly error when package doesn't exist

pkg/apiserver/registry/datapackaging/package_crd_rest_test.go

@@ -146,6 +146,7 @@ func TestPackageVersionGetPresentInOnlyNS(t *testing.T) {
 func TestPackageVersionGetNotFound(t *testing.T) {
 	namespacedPackageVersion := excludedNonGlobalIntPackageVersion()
 	name := namespacedPackageName
+	expectedError := "package.data.packaging.carvel.dev \"" + name + "\" not found"
 
 	internalClient := fake.NewSimpleClientset(namespacedPackageVersion)
 	fakeCoreClient := k8sfake.NewSimpleClientset(namespace())
@@ -157,8 +158,8 @@ func TestPackageVersionGetNotFound(t *testing.T) {
 		t.Fatalf("Expected get operation to fail, but it didn't")
 	}
 
-	if !errors.IsNotFound(err) {
-		t.Fatalf("Expected a not found error, got: %v", err)
+	if !errors.IsNotFound(err) || err.Error() != expectedError {
+		t.Fatalf("Expected error : %s, got: %v", expectedError, err)
 	}
 
 }

pkg/apiserver/registry/datapackaging/package_storage_client.go

@@ -152,7 +152,24 @@ func (t PackageTranslator) ToExternalWatcher(intObjWatcher watch.Interface, fiel
 }
 
 func (t PackageTranslator) ToExternalError(err error) error {
-	// TODO: implement
+	statusErr := err.(*errors.StatusError)
+
+	if statusErr.ErrStatus.Details.Kind == "internalpackages" && statusErr.ErrStatus.Details.Group == internalpkgingv1alpha1.SchemeGroupVersion.Group {
+		packageName, err := t.ToExternalName(statusErr.ErrStatus.Details.Name)
+		if err != nil {
+			return err
+		}
+
+		switch statusErr.ErrStatus.Reason {
+		case metav1.StatusReasonNotFound:
+			return errors.NewNotFound(datapkgingv1alpha1.Resource("package"), packageName)
+		case metav1.StatusReasonAlreadyExists:
+			return errors.NewAlreadyExists(datapkgingv1alpha1.Resource("package"), packageName)
+		default:
+			return err
+		}
+	}
+
 	return err
 }