Ticket #6983: base.py.patch

main.py

@@ -133 +133 @@
         if max([bool(f.errors()) for f in self.form_fields]):
             classes.append('error')
         if classes:
-            self.cell_class_attribute = u' class="%s" ' % ' '.join(classes)
+            self.cell_class_attribute = mark_safe(u' class="%s" ' % ' '.join(classes))
         self._repr_filled = False
 
         if field.rel: