Ensure to_dict() supports unicode

When we compose a string for user_identity, we should
ensure that we don't break for non-ascii strings in
user name or tenant name or domain names.

Change-Id: Id457ebe415f78c435fc8ece810f0a1b20964dabf
Closes-Bug: #1507937

oslo_context/context.py

@@ -48,7 +48,7 @@ class RequestContext(object):
     accesses the system, as well as additional request information.
     """
 
-    user_idt_format = '{user} {tenant} {domain} {user_domain} {p_domain}'
+    user_idt_format = u'{user} {tenant} {domain} {user_domain} {p_domain}'
 
     def __init__(self, auth_token=None, user=None, tenant=None, domain=None,
                  user_domain=None, project_domain=None, is_admin=False,

oslo_context/tests/test_context.py

@@ -1,3 +1,4 @@
+# -*- encoding: utf-8 -*-
 # Copyright 2011 OpenStack Foundation.
 # All Rights Reserved.
 #
@@ -177,7 +178,8 @@ class ContextTest(test_base.BaseTestCase):
 
     def test_values(self):
         auth_token = "token1"
-        user = "user1"
+        # test unicode support
+        user = u"John Gāo"
         tenant = "tenant1"
         domain = "domain1"
         user_domain = "user_domain1"