Update to LibSass v3.6.3

Fixes #6862

resources/resource.go

@@ -22,6 +22,10 @@ import (
 	"path/filepath"
 	"sync"
 
+	"github.com/gohugoio/hugo/resources/internal"
+
+	"github.com/gohugoio/hugo/common/herrors"
+
 	"github.com/gohugoio/hugo/hugofs"
 
 	"github.com/gohugoio/hugo/media"
@@ -95,6 +99,24 @@ type Transformer interface {
 	Transform(...ResourceTransformation) (ResourceTransformer, error)
 }
 
+func NewFeatureNotAvailableTransformer(key string, elements ...interface{}) ResourceTransformation {
+	return transformerNotAvailable{
+		key: internal.NewResourceTransformationKey(key, elements...),
+	}
+}
+
+type transformerNotAvailable struct {
+	key internal.ResourceTransformationKey
+}
+
+func (t transformerNotAvailable) Transform(ctx *ResourceTransformationCtx) error {
+	return herrors.ErrFeatureNotAvailable
+}
+
+func (t transformerNotAvailable) Key() internal.ResourceTransformationKey {
+	return t.key
+}
+
 type baseResourceResource interface {
 	resource.Cloner
 	resource.ContentProvider