Improve handling of empty resource_registry

It's possible that content["resource_registry"] might
not exist or be iterable so wrap the reference to it
with a try/except for a KeyError or TypeError and continue
the deployment without the empty resource_registry instead
of failing.

Change-Id: Ic7d88382a0ff15c24800f12ddbf69f13d6804b28
Closes-Bug: #1833743

tripleoclient/utils.py

@@ -1876,14 +1876,15 @@ def check_file_for_enabled_service(env_file):
         content = yaml.load(open(env_file))
         deprecated_services_enabled = []
         for service in constants.DEPRECATED_SERVICES.keys():
-            if ("resource_registry" in content and
-                    service in content["resource_registry"]):
+            try:
                 if content["resource_registry"][service] != "OS::Heat::None":
                     LOG.warn("service " + service + " is enabled in "
                              + str(env_file) + ". " +
                              constants.DEPRECATED_SERVICES[service])
                     deprecated_services_enabled.append(service)
-
+            except (KeyError, TypeError) as e:
+                # ignore if content["resource_registry"] is empty
+                pass
         if deprecated_services_enabled:
             confirm = prompt_user_for_confirmation(
                 message="Do you still wish to continue with deployment [y/N]",