Fix file extension getter.

opengever/exportng/sync.py

@@ -13,7 +13,6 @@
 from plone.dexterity.utils import iterSchemata
 from zope.schema import getFields
 import logging
-import os.path
 
 
 logger = logging.getLogger('opengever.exportng')
@@ -62,9 +61,7 @@ def get_filedata(obj, attrname):
 
 
 def get_file_extension(obj, attrname):
-    value = getattr(obj, attrname)
-    if value is not None:
-        return os.path.splitext(value.filename)[-1][1:]
+    return obj.get_file_extension()
 
 
 def userid_to_email(obj, attrname):