Captures activation errors for WP plugins

wp-plugin-activation-error.php

<?php
// https://www.toddlahman.com/the-plugin-generated-x-characters-of-unexpected-output-during-activation/
function plugin_activate_save_error() {
    ob_clean();
    update_option( 'plugin_error',  ob_get_contents() );
}
add_action( 'activated_plugin', 'plugin_activate_save_error' );
/* Then to display the error message: */
echo get_option( 'plugin_error' );