flask: error_handler for blueprints

You can use Blueprint.app_errorhandler method like this:

bp = Blueprint('errors', __name__)

@bp.app_errorhandler(404)
def handle_404(err):
    return render_template('404.html'), 404

@bp.app_errorhandler(500)
def handle_500(err):
    return render_template('500.html'), 500