Added missing import for SkipTest in test_authorization.

Fixes bug 1058281

Change-Id: I41d706aeb67c9555bee0113247855b4a077775eb
diff --git a/tempest/tests/compute/test_authorization.py b/tempest/tests/compute/test_authorization.py
index 3f2feec..12fa94b 100644
--- a/tempest/tests/compute/test_authorization.py
+++ b/tempest/tests/compute/test_authorization.py
@@ -17,6 +17,7 @@
 
 from nose.plugins.attrib import attr
 from nose.tools import raises
+from nose import SkipTest
 import unittest2 as unittest
 
 from tempest import openstack
@@ -32,7 +33,7 @@
     def setUpClass(cls):
         if not compute.MULTI_USER:
             msg = "Need >1 user"
-            raise nose.SkipTest(msg)
+            raise SkipTest(msg)
 
         super(AuthorizationTest, cls).setUpClass()