docs: def get_contents(self, origin):
          """
          Try to load the origin.
          """
          try:
              path = self.get_app_template_path(
                  origin.app_name, origin.template_name)
              with io.open(path, encoding=self.engine.file_charset) as fp:
                  return fp.read()
          except KeyError:
              raise TemplateDoesNotExist(origin)
          except IOError as error:
              if error.errno == errno.ENOENT:
                  raise TemplateDoesNotExist(origin)
              raise