Change tempest NotFound exc to tempest-lib exc

This commit changes tempest.exceptions.NotFound to
tempest_lib.exceptions.NotFound. This is one of the migrating
rest client to tempest-lib works.

Change-Id: I2be04f600e6bd8d7d78948d25395d8e04fa0dea3
diff --git a/tempest/api/identity/admin/test_services.py b/tempest/api/identity/admin/test_services.py
index 03d6e35..30e0058 100644
--- a/tempest/api/identity/admin/test_services.py
+++ b/tempest/api/identity/admin/test_services.py
@@ -14,10 +14,10 @@
 #    under the License.
 
 from six import moves
+from tempest_lib import exceptions as lib_exc
 
 from tempest.api.identity import base
 from tempest.common.utils import data_utils
-from tempest import exceptions
 from tempest import test
 
 
@@ -28,7 +28,7 @@
         # Deleting the service created in this method
         self.client.delete_service(service_id)
         # Checking whether service is deleted successfully
-        self.assertRaises(exceptions.NotFound, self.client.get_service,
+        self.assertRaises(lib_exc.NotFound, self.client.get_service,
                           service_id)
 
     @test.attr(type='smoke')