Return filename that contains specific language resource name.

  Args:
    name (string): Name of the resource.
    lang (string): language code to be loaded.

def locate_resource(name, lang, filter=None):
  """Return filename that contains specific language resource name.

  Args:
    name (string): Name of the resource.
    lang (string): language code to be loaded.
  """
  task_dir = resource_dir.get(name, name)
  package_id = u"{}.{}".format(task_dir, lang)
  p = path.join(polyglot_path, task_dir, lang)
  if not path.isdir(p):
    if downloader.status(package_id) != downloader.INSTALLED:
      raise ValueError("This resource is available in the index "
                       "but not downloaded, yet. Try to run\n\n"
                       "polyglot download {}".format(package_id))
  return path.join(p, os.listdir(p)[0])