an import was missing (used line 1416)

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@26925 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/Formulator/Widget.py

@@ -5,6 +5,7 @@ from DateTime import DateTime
 from cgi import escape
 import types
 from DocumentTemplate.ustr import ustr
+from urlparse import urljoin
 
 class Widget:
   """A field widget that knows how to display itself as HTML.