def parse_auth_token_from_request(self, auth_header):
        """
        Parses and returns the Hawk Authorization header if it is present and well-formed.
        Raises `falcon.HTTPUnauthoried exception` with proper error message
        """
        if not auth_header:
            raise falcon.HTTPUnauthorized(
                description='Missing Authorization Header')

        try:
            auth_header_prefix, _ = auth_header.split(' ', 1)
        except ValueError:
            raise falcon.HTTPUnauthorized(
                description='Invalid Authorization Header: Missing Scheme or Parameters')

        if auth_header_prefix.lower() != self.auth_header_prefix.lower():
            raise falcon.HTTPUnauthorized(
                description='Invalid Authorization Header: '
                            'Must start with {0}'.format(self.auth_header_prefix))

        return auth_header
Parses and returns the Hawk Authorization header if it is present and well-formed.
        Raises `falcon.HTTPUnauthoried exception` with proper error message