Fix masking of error when creating index

.gitignore

@@ -4,6 +4,8 @@
 .#*
 .project
 .settings
+**/.idea/
+**/*.iml
 .DS_Store
 /analysis/token_filters/cld2/cld2-read-only
 /analysis/token_filters/cld2/libcld2_full.a

index_meta.go

@@ -58,7 +58,10 @@ func (i *indexMeta) Save(path string) (err error) {
 	// ensure any necessary parent directories exist
 	err = os.Mkdir(path, 0700)
 	if err != nil {
-		return ErrorIndexPathExists
+		if os.IsExist(err) {
+			return ErrorIndexPathExists
+		}
+		return err
 	}
 	metaBytes, err := json.Marshal(i)
 	if err != nil {