致命错误：找不到类“ DB \ Exception”

Question

我下载了opencart 2.3.0.2。我想上传一个运输跟踪模块。我复制了文件并从用户组激活，但是当我要编辑扩展名时出现此错误；

（！）致命错误：在第40行的C：\ wamp64 \ www \ opencard \ system \ library \ db \ mysqli.php中找不到类'DB \ Exception'

这是我的mysqli.php代码

<?php
class DB {
private $adaptor;

public function __construct($adaptor, $hostname, $username, $password, 
$database, $port = NULL) {
    $class = 'DB\\' . $adaptor;

    if (class_exists($class)) {
        $this->adaptor = new $class($hostname, $username, $password, $database, $port);
    } else {
        throw new \Exception('Error: Could not load database adaptor ' . $adaptor . '!');
    }
}

public function query($sql, $params = array()) {
    return $this->adaptor->query($sql, $params);
}

public function escape($value) {
    return $this->adaptor->escape($value);
}

public function countAffected() {
    return $this->adaptor->countAffected();
}

public function getLastId() {
    return $this->adaptor->getLastId();
}

public function connected() {
    return $this->adaptor->connected();
 }
 }

能帮我吗？我能做什么。 ：）