--- a/devtools/fake.py	Wed Sep 16 11:23:51 2015 +0200
+++ b/devtools/fake.py	Mon Sep 14 16:03:07 2015 +0200
@@ -22,6 +22,8 @@
 
 from contextlib import contextmanager
 
+from six import string_types
+
 from logilab.database import get_db_helper
 
 from cubicweb.req import RequestSessionBase
@@ -91,7 +93,7 @@
 
     def set_request_header(self, header, value, raw=False):
         """set an incoming HTTP header (for test purpose only)"""
-        if isinstance(value, basestring):
+        if isinstance(value, string_types):
             value = [value]
         if raw:
             # adding encoded header is important, else page content