Use OutputDefinition to generate attributes schema

We have the OutputDefinition API now, and no longer need to treat
templates like CFN JSON blobs to obtain information about outputs.

Change-Id: I8dfea1e9855a56fb85d2e3af40996d5f337d7859

heat/engine/attributes.py

@@ -200,11 +200,9 @@ class Attributes(collections.Mapping):
         return outp
 
     @staticmethod
-    def schema_from_outputs(json_snippet):
+    def schema_from_outputs(outputs):
-        if json_snippet:
+        return dict((o.name, Schema(o.description()))
-            return dict((k, Schema(v.get("Description")))
+                    for o in outputs.values())
-                        for k, v in json_snippet.items())
-        return {}
 
     def _validate_type(self, attrib, value):
         if attrib.schema.type == attrib.schema.STRING:

heat/engine/resources/stack_resource.py

@@ -92,8 +92,8 @@ class StackResource(resource.Resource):
 
         return "nested_stack"
 
-    def _outputs_to_attribs(self, json_snippet):
+    def _outputs_to_attribs(self, parsed_template):
-        outputs = json_snippet.get('Outputs')
+        outputs = parsed_template.outputs(None)
         if not self.attributes and outputs:
             self.attributes_schema = (
                 attributes.Attributes.schema_from_outputs(outputs))

heat/engine/resources/template_resource.py

@@ -108,7 +108,7 @@ class TemplateResource(stack_resource.StackResource):
         return ((properties.Properties.schema_from_params(
                 tmpl.param_schemata(param_defaults))),
                 (attributes.Attributes.schema_from_outputs(
-                 tmpl[tmpl.OUTPUTS])))
+                 tmpl.outputs(None))))
 
     def _generate_schema(self):
         self._parsed_nested = None