admin_notices not working in post editor

So it looks like there is some page redirecting going on in the post updating process, hence why I can’t even access a $GLOBALS variable. The only alternative I found to use was to use a session variable. Something like:

add_filter( 'pre_insert_term', 'pre_insert_term_action', 10, 2 );
add_action( 'admin_notices', 'show_example_error' );

function pre_insert_term_action( $term, $taxonomy ) {
    if ( MY CONDITION THAT WARRANTS A WARNING NOTICE IS TRUE ) {
        if ( session_id() === '' || ! isset($_SESSION) ) {
            session_start();
        }
        $_SESSION['show_my_error_message'] = true;
        return new WP_Error( 'code', 'message' );
    }
    return $term;
}

function show_example_error() {
    if ( session_id() === '' || ! isset($_SESSION) ) {
        session_start();
    }
    if ( isset($_SESSION['show_my_error_message']) ) {
        ?>
        <div class="error">
            <p>My example warning message.</p>
        </div>
        <?php
        unset($_SESSION['show_my_error_message']);
    }
}