Fix user field rendering when no person associated

tailbone/forms/renderers/users.py

@@ -26,6 +26,8 @@ User Field Renderers
 
 from __future__ import unicode_literals, absolute_import
 
+import six
+
 from rattail.db import model
 from rattail.db.auth import has_permission, administrator_role
 
@@ -44,7 +46,7 @@ class UserFieldRenderer(formalchemy.TextFieldRenderer):
         user = self.raw_value
         if not user:
             return ''
-        title = user.display_name
+        title = six.text_type(user)
         if kwargs.get('hyperlink') and self.request.has_perm('users.view'):
             return tags.link_to(title, self.request.route_url('users.view', uuid=user.uuid))
         return title