Add accessor method to pull URLs from the catalog

It's handy sometimes and the specifics of how to do so is complex.

Change-Id: I90d5c8c2709cf9d8bd76c3dbcbe171c7d75572a8

releasenotes/notes/endpoint-from-catalog-bad36cb0409a4e6a.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - Add new method, 'endpoint_for' which will return the
+    raw endpoint for a given service from the current catalog.

shade/openstackcloud.py

@@ -566,9 +566,17 @@ class OpenStackCloud(_normalize.Normalizer):
         return self._keystone_client
 
     @property
-    def service_catalog(self):
+    def _keystone_catalog(self):
         return self.keystone_session.auth.get_access(
-            self.keystone_session).service_catalog.catalog
+            self.keystone_session).service_catalog
+
+    @property
+    def service_catalog(self):
+        return self._keystone_catalog.catalog
+
+    def endpoint_for(self, service_type, interface='public'):
+        return self._keystone_catalog.url_for(
+            service_type=service_type, interface=interface)
 
     @property
     def auth_token(self):

shade/tests/unit/base.py

@@ -122,11 +122,8 @@ class RequestsMockTestCase(BaseTestCase):
 
     def get_mock_url(self, service_type, interface, resource=None,
                      append=None, base_url_append=None):
-        service_catalog = self.cloud.keystone_session.auth.get_access(
-            self.cloud.keystone_session).service_catalog
-        endpoint_url = service_catalog.url_for(
-            service_type=service_type,
-            interface=interface)
+        endpoint_url = self.cloud.endpoint_for(
+            service_type=service_type, interface=interface)
         to_join = [endpoint_url]
         if base_url_append:
             to_join.append(base_url_append)