I am using OS::Heat::ResourceGroup, I would like to use the same outer template with multiple different nested templates. To achieve this I would like to pass the location(URL) of the nested YAML as a parameter(see below). However I get the following error.

ERROR: Failed to validate: Could not fetch remote template "http://localhost/testdef.yaml": Failed to retrieve template: None: Max retries exceeded with url: /testdef.yaml (Caused by None)

When I hardcode the YAML location all works fine. Is it possible to do what I am trying to achieve.

description: test template
heat_template_version: 2015-04-30
parameters:
  file_name:
    type: string
    default: http://localhost/testdef.yaml
  instances:
    type: string
    default: 2
resources:
  auto_scaling_group:
    type: OS::Heat::ResourceGroup
    properties:
      count: { get_param: instances }
      resource_def:
        type: {get_param: file_name}
        #type: http://localhost/testdef.yaml
        properties:
          index: '%index%'