Additional uncaught exception thrown while handling exception.

<h1>Additional uncaught exception thrown while handling exception.</h1><h2>Original</h2><p>PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT r.filename AS filename
FROM 
{registry} r
WHERE  (r.name LIKE :db_condition_placeholder_0 ESCAPE &amp;#039;\\&amp;#039;) AND (r.type = :db_condition_placeholder_1) ; Array
(
    [:db_condition_placeholder_0] =&amp;gt; Drupal\\xautoload\\DrupalSystem\\DrupalSystemInterface
    [:db_condition_placeholder_1] =&amp;gt; trait
)
 in _registry_check_code() (line 3492 of /var/www/html/includes/bootstrap.inc).</p><h2>Additional</h2><p>PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT r.filename AS filename
FROM 
{registry} r
WHERE  (r.name LIKE :db_condition_placeholder_0 ESCAPE &amp;#039;\\&amp;#039;) AND (r.type = :db_condition_placeholder_1) ; Array
(
    [:db_condition_placeholder_0] =&amp;gt; Drupal\\xautoload\\Phases\\PhaseObserverInterface
    [:db_condition_placeholder_1] =&amp;gt; trait
)
 in _registry_check_code() (line 3492 of /var/www/html/includes/bootstrap.inc).</p><hr />