Indicate to the client that it needs to authenticate via a 401.

def authenticate(self):
        """
        Indicate to the client that it needs to authenticate via a 401.
        """
        if request.headers.get('Authorization') or request.args.get('access_token'):
            realm = 'Bearer realm="%s", error="invalid_token"' % __package__
        else:
            realm = 'Bearer realm="%s"' % __package__
        resp = Response(None, 401, {'WWW-Authenticate': realm})
        abort(401, description='Please provide proper credentials', response=resp)