<?php
//...

register_activation_hook(__FILE__, 'myplugin_activate');

if('error_scrape' == $_GET['action']) {
  //...
  echo get_option('myplugin_activate_error');
  delete_option('myplugin_activate_error');
  deactivate_plugins($_GET['plugin']);
  die();
}

function myplugin_activate() {
  //...

  if($error) {
    add_option('myplugin_activate_error', $error);
    //trigger a fatal error
    trigger_error('', E_USER_ERROR);
  }
}
?>