Add a preferred_language method to relation widget, to ease overriding

views/widgets.py

@@ -45,7 +45,7 @@ else:
             languages = set(lang for lang, in self._cw.execute(
                 'DISTINCT Any OLC WHERE ' + baserql + ', O preferred_label OL, '
                 'OL language_code OLC', args))
-            for lang in (self._cw.lang, 'en', None):
+            for lang in self.preferred_languages():
                 if lang in languages:
                     break
             else:
@@ -70,6 +70,10 @@ else:
             entity = self.compute_entity()
             return entity.e_schema.rdef(rtype, role, tetype)
 
+        def preferred_languages(self):
+            """Return language by order of preference."""
+            return (self._cw.lang, 'en', None)
+
         @staticmethod
         def pref_label_label(concept):
             return concept.cw_rset[concept.cw_row][2]