--- a/cubicweb/web/http_headers.py	Fri Apr 05 17:21:14 2019 +0200
+++ b/cubicweb/web/http_headers.py	Fri Apr 05 17:58:19 2019 +0200
@@ -6,9 +6,7 @@
 from calendar import timegm
 import base64
 import re
-
-from six import string_types
-from six.moves.urllib.parse import urlparse
+from urllib.parse import urlparse
 
 
 def dashCapitalize(s):
@@ -383,7 +381,7 @@
 
 def unique(seq):
     '''if seq is not a string, check it's a sequence of one element and return it'''
-    if isinstance(seq, string_types):
+    if isinstance(seq, str):
         return seq
     if len(seq) != 1:
         raise ValueError('single value required, not %s' % seq)
@@ -455,10 +453,10 @@
 
     """
     if (value in (True, 1) or
-            isinstance(value, string_types) and value.lower() == 'true'):
+            isinstance(value, str) and value.lower() == 'true'):
         return 'true'
     if (value in (False, 0) or
-            isinstance(value, string_types) and value.lower() == 'false'):
+            isinstance(value, str) and value.lower() == 'false'):
         return 'false'
     raise ValueError("Invalid true/false header value: %s" % value)