docs: def resource_spec(opts):
      """
      Return the spec (URL, package spec, file, etc) for a named resource.
      """
      resources = _load(opts.resources, opts.output_dir)
      if opts.resource_name not in resources:
          sys.stderr.write('Invalid resource name: {}\n'.format(opts.resource_name))
          return 1
      print(resources[opts.resource_name].spec)