erp5_core: Fix unicode bug on ZODB History view.

Some objects become unicode when %s is applied and may cause
UnicodeDecodeError, thus use %r insead.

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_core/Base_getZODBHistoryList.py

@@ -16,7 +16,7 @@ def beautifyChange(change_dict):
         six.text_type(property_value, 'utf-8')
       except UnicodeDecodeError:
         property_value = '(binary)'
-    change_list.append('%s:%s' % (property_name, property_value))
+    change_list.append('%s:%r' % (property_name, property_value))
   return change_list
 
 try: