add const

weed/filer2/etcd/etcd_store.go

@@ -2,6 +2,7 @@ package etcd
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -136,7 +137,7 @@ func (store *EtcdStore) DeleteFolderChildren(ctx context.Context, fullpath weed_
 }
 
 func (store *EtcdStore) ListDirectoryPrefixedEntries(ctx context.Context, fullpath weed_util.FullPath, startFileName string, inclusive bool, limit int, prefix string) (entries []*filer2.Entry, err error) {
-	return nil, fmt.Errorf("UNSUPPORTED")
+	return nil, errors.New(filer2.UnsupportedListDirectoryPrefixedErr)
 }
 
 func (store *EtcdStore) ListDirectoryEntries(ctx context.Context, fullpath weed_util.FullPath, startFileName string, inclusive bool, limit int) (entries []*filer2.Entry, err error) {