Add support for testing custom RBAC requirements

Add support of running Patrole against a custom requirements YAML that
defines RBAC requirements. The YAML file lists all the APIs and the roles
that should have access to the APIs. The purpose of running Patrole against
a requirements YAML is to verify that the RBAC policy is in accordance to
deployment specific requirements. Running Patrole against a requirements
YAML is completely optional and can be enabled through the rbac section of
the tempest.conf.

Change-Id: I8ba89ab5e134b15e97ac20a7aacbfd70896e192f
Implements: blueprint support-custom-yaml
Co-Authored-By: Sangeet Gupta <sg774j@att.com>
Co-Authored-By: David Purcell <d.purcell222@gmail.com>
diff --git a/patrole_tempest_plugin/rbac_policy_parser.py b/patrole_tempest_plugin/rbac_policy_parser.py
index bb34f6c..17a626c 100644
--- a/patrole_tempest_plugin/rbac_policy_parser.py
+++ b/patrole_tempest_plugin/rbac_policy_parser.py
@@ -25,12 +25,13 @@
 from tempest.common import credentials_factory as credentials
 
 from patrole_tempest_plugin import rbac_exceptions
+from patrole_tempest_plugin.rbac_utils import RbacAuthority
 
 CONF = cfg.CONF
 LOG = logging.getLogger(__name__)
 
 
-class RbacPolicyParser(object):
+class RbacPolicyParser(RbacAuthority):
     """A class for parsing policy rules into lists of allowed roles.
 
     RBAC testing requires that each rule in a policy file be broken up into