Return JSON for Unauthorized message

To be consistent with how keystone formats 401 responses,
keystonemiddleware should also return JSON when auth_token fails to
authenticate. This patch modifies the response to use the
application/json Content-Type and formats the body in the same way that
keystone does[1]

[1] http://git.openstack.org/cgit/openstack/keystone/tree/keystone/common/wsgi.py?h=9.0.0&id=3e5fca06c6b7dd6060721faa39428b133edd10f0#n812

Change-Id: I6601862ef948b50dedba033c03a42acedbfc8d90
Closes-bug: #1367062

keystonemiddleware/auth_token/__init__.py

@@ -751,9 +751,16 @@ class AuthProtocol(BaseAuthProtocol):
                 self.log.info(_LI('Deferring reject downstream'))
             else:
                 self.log.info(_LI('Rejecting request'))
+                message = 'The request you have made requires authentication.'
+                body = {'error': {
+                    'code': 401,
+                    'title': 'Unauthorized',
+                    'message': message,
+                }}
                 raise webob.exc.HTTPUnauthorized(
-                    body='Authentication required',
-                    headers=self._reject_auth_headers)
+                    body=jsonutils.dumps(body),
+                    headers=self._reject_auth_headers,
+                    content_type='application/json')
 
         if request.user_token_valid:
             user_auth_ref = request.token_auth._user_auth_ref

keystonemiddleware/tests/unit/auth_token/test_auth_token_middleware.py

@@ -1925,7 +1925,8 @@ class CommonCompositeAuthTests(object):
         resp = self.call_middleware(headers={'X-Auth-Token': token,
                                              'X-Service-Token': service_token},
                                     expected_status=401)
-        self.assertEqual(b'Authentication required', resp.body)
+        expected_body = b'The request you have made requires authentication.'
+        self.assertThat(resp.body, matchers.Contains(expected_body))
 
     def test_composite_auth_no_service_token(self):
         self.purge_service_token_expected_env()
@@ -1952,13 +1953,15 @@ class CommonCompositeAuthTests(object):
         resp = self.call_middleware(headers={'X-Auth-Token': token,
                                              'X-Service-Token': service_token},
                                     expected_status=401)
-        self.assertEqual(b'Authentication required', resp.body)
+        expected_body = b'The request you have made requires authentication.'
+        self.assertThat(resp.body, matchers.Contains(expected_body))
 
     def test_composite_auth_no_user_token(self):
         service_token = self.token_dict['uuid_service_token_default']
         resp = self.call_middleware(headers={'X-Service-Token': service_token},
                                     expected_status=401)
-        self.assertEqual(b'Authentication required', resp.body)
+        expected_body = b'The request you have made requires authentication.'
+        self.assertThat(resp.body, matchers.Contains(expected_body))
 
     def test_composite_auth_delay_ok(self):
         self.middleware._delay_auth_decision = True