diff -r 6b3523f81f42 -r 26744ad37953 cubicweb/ext/test/unittest_rest.py
--- a/cubicweb/ext/test/unittest_rest.py	Fri Apr 05 17:21:14 2019 +0200
+++ b/cubicweb/ext/test/unittest_rest.py	Fri Apr 05 17:58:19 2019 +0200
@@ -15,7 +15,6 @@
 #
 # You should have received a copy of the GNU Lesser General Public License along
 # with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
-from six import PY3
 
 from logilab.common.testlib import unittest_main
 from cubicweb.devtools.testlib import CubicWebTC
@@ -93,8 +92,7 @@
             context = self.context(req)
             out = rest_publish(context, ':rql:`Any X WHERE X is CWUser:toto`')
             self.assertTrue(out.startswith("<p>an error occurred while interpreting this "
-                                           "rql directive: ObjectNotFound(%s'toto'" %
-                                           ('' if PY3 else 'u')),
+                                           "rql directive: ObjectNotFound('toto'"),
                             out)
 
     def test_rql_role_without_vid(self):