Fix rbac_rule_validation log statement raises TypeError

If an OverPermission error occurs, then the LOG.error statement
that should execute throws a TypeError due to a minor syntax issue.

Example: http://logs.openstack.org/31/466331/6/check/gate-tempest-dsvm-patrole-member-ubuntu-xenial/dc38b01/console.html

Change-Id: I3f7fde708521cfd200fd0835a6f2d697ed83b08b
Closes-Bug: #1693297
diff --git a/patrole_tempest_plugin/rbac_rule_validation.py b/patrole_tempest_plugin/rbac_rule_validation.py
index 60a0f10..c63ef90 100644
--- a/patrole_tempest_plugin/rbac_rule_validation.py
+++ b/patrole_tempest_plugin/rbac_rule_validation.py
@@ -116,7 +116,7 @@
             else:
                 if not allowed:
                     LOG.error("Role %s was allowed to perform %s",
-                              (role, rule))
+                              role, rule)
                     raise rbac_exceptions.RbacOverPermission(
                         "OverPermission: Role %s was allowed to perform %s" %
                         (role, rule))