Fix an unbound variable in setup_package.

This resolves an unbound variable bug that users can hit
when running tempest without a second user account:

Change-Id: Id36f9c29be8db67de4089df2f0182194cf0fa482
UnboundLocalError: local variable 'e' referenced before assignment
diff --git a/tempest/tests/compute/__init__.py b/tempest/tests/compute/__init__.py
index 1384ee3..fd6912d 100644
--- a/tempest/tests/compute/__init__.py
+++ b/tempest/tests/compute/__init__.py
@@ -75,6 +75,6 @@
             user2_tenant_name = CONFIG.compute.alt_tenant_name
             if not user2_password or user2_tenant_name:
                 msg = ("Alternate user specified but not alternate "
-                       "tenant or password") % e
+                       "tenant or password")
                 raise nose.SkipTest(msg)
             MULTI_USER = True