[test] fix unittest_registration

probably due to lxml upgrade

test/unittest_registration.py

@@ -60,14 +60,14 @@ class RegistrationTC(CubicWebTC):
         req = self.request()
         req.form = {'firstname-subject': u'Toto'}
         pageinfo = self.view('registration', req=req, rset=None)
-        ns = {'ns': pageinfo.default_ns}
+
         # check form field names
-        names = pageinfo.etree.xpath('//ns:form[@id="registrationForm"]//ns:input[@type!="hidden"]/@name',
-                                     namespaces=ns)
+        names = pageinfo.etree.xpath('//form[@id="registrationForm"]//input[@type!="hidden"]/@name')
+        print "*"*60, pageinfo.etree.__class__
         self.assertEqual(set(names), set(self.data))
+
         # check form field value
-        firstname = pageinfo.etree.xpath('//ns:input[@name="firstname-subject"]/@value',
-                                         namespaces=ns)
+        firstname = pageinfo.etree.xpath('//input[@name="firstname-subject"]/@value')
         self.assertEqual(firstname, [req.form['firstname-subject']])
 
     def test_send_mail_ok(self):