--- a/misc/migration/bootstrapmigration_repository.py	Tue Sep 15 18:30:05 2015 +0200
+++ b/misc/migration/bootstrapmigration_repository.py	Tue Sep 15 18:39:09 2015 +0200
@@ -21,6 +21,8 @@
 """
 from __future__ import print_function
 
+from six import text_type
+
 from cubicweb import ConfigurationError
 from cubicweb.server.session import hooks_control
 from cubicweb.server import schemaserial as ss
@@ -149,7 +151,7 @@
                 default = yams.DATE_FACTORY_MAP[atype](default)
         else:
             assert atype == 'String', atype
-            default = unicode(default)
+            default = text_type(default)
         return Binary.zpickle(default)
 
     dbh = repo.system_source.dbhelper