Redirect contact form on submit Using Drupal 8 and trying to get the contact form to redirect to the same page after submitting. By default it seem to redirect to the home page.

I have edited my themename.theme file

function themename_form_alter(&amp;$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {

  //contact page form
  if ($form_id == 'contact_message_feedback_form') {
    $url = Url::fromRoute('contact.site_page');
    $form_state-&gt;setRedirectUrl($url);
  }
}


This throws a bunch of mysql errors. Like so:

Uncaught exception thrown in session handler.

Drupal\Core\Database\DatabaseExceptionWrapper: SQLSTATE[08S01]: Communication link failure: 1153 Got a packet bigger than 'max_allowed_packet' bytes: UPDATE {sessions} SET uid=:db_update_placeholder_0, hostname=:db_update_placeholder_1, session=:db_update_placeholder_2, timestamp=:db_update_placeholder_3 WHERE ( (sid = :db_condition_placeholder_0) ); Array ( [:db_update_placeholder_0] =&gt; 1 [:db_update_placeholder_1] =&gt; ::1 [:db_update_placeholder_2] =&gt; _sf2_attributes|a:1:{s:3:"uid";s:1:"1";}_sf2_flashes|a:0:{}_sf2_meta|a:4:{s:1:"u";i:1454074283;s:1:"c";i:1452243053;s:1:"l";s:7:"2000000";s:1:"s";s:43:"dVseXv540u6wL5GZm_gs6fzuP9qtck-j5A5lexqnaQE";}authorize_page_title|O:48:"Drupal\Core\StringTranslation\TranslatableMarkup":3:{s:9:"*string";s:14:"Update manager";s:12:"*arguments";a:0:{}s:10:"*options";a:0:{}}messages|a:1:{s:6:"status";a:2:{i:0;O:25:"Drupal\Core\Render\Markup":1:{s:9:"*string";s:1020035:"&lt;script class="-kint-js"&gt;(function(){if("undefined"===typeof kintInitialized){kintInitialized=1;var e=[],f=-1,g=function(b){var a=window in Drupal\Core\Session\SessionHandler-&gt;write() (line 89 of /Users/timmcdonald/Code/waypoint/v3/core/lib/Drupal/Core/Session/SessionHandler.php).


and other errors.
Is there something I am missing?
Here is what I ended up doing in a custom module if anyone else needs to do this


use Drupal\Core\Url;

function custom_module_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {

  //contact page form
  if ($form_id == 'contact_message_feedback_form') {
    $form['actions']['submit']['#submit'][] = 'custom_module_contact_submit';
    dpm($form['actions']['submit']);
  }

}

function custom_module_contact_submit(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
    drupal_set_message('we sent a form woohoo');
    $url = Url::fromRoute('contact.site_page');
    $form_state->setRedirectUrl($url);
}