Ensure that LocalizedError are returned by parsers

reader/feed/rss/parser_test.go

@@ -8,6 +8,8 @@ import (
 	"bytes"
 	"testing"
 	"time"
+
+	"github.com/miniflux/miniflux2/errors"
 )
 
 func TestParseRss2Sample(t *testing.T) {
@@ -541,4 +543,8 @@ func TestParseInvalidXml(t *testing.T) {
 	if err == nil {
 		t.Error("Parse should returns an error")
 	}
+
+	if _, ok := err.(errors.LocalizedError); !ok {
+		t.Error("The error returned must be a LocalizedError")
+	}
 }