在symfony4和dority中尝试使用pdo\umysql驱动程序时，我运行 $entityManager->flush(); 我要走了 An exception occurred in driver: could not find driver 输出：

Doctrine\DBAL\Exception\DriverException:
An exception occurred in driver: could not find driver

  at vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php:125
  at Doctrine\DBAL\Driver\AbstractMySQLDriver->convertException('An exception occurred in driver: could not find driver', object(PDOException))
     (vendor/doctrine/dbal/lib/Doctrine/DBAL/DBALException.php:184)
  at Doctrine\DBAL\DBALException::wrapException(object(Driver), object(PDOException), 'An exception occurred in driver: could not find driver')
     (vendor/doctrine/dbal/lib/Doctrine/DBAL/DBALException.php:169)
  at Doctrine\DBAL\DBALException::driverException(object(Driver), object(PDOException))
     (vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/PDOMySql/Driver.php:47)

.env文件 DATABASE_URL=mysql://USER:PASSWORD!@HOSTNAME/DATABASE 条令.yml

doctrine:
    dbal:
        # configure these for your database server
        driver: 'pdo_mysql'
        server_version: '5.7.21'
        charset: utf8mb4
        default_table_options:
            charset: utf8mb4
            collate: utf8mb4_unicode_ci

我已经确保docker php fpm容器具有正确的模块。

root@644cfdc6b45b:/usr/local/etc/php/conf.d# php -m | grep -i pdo
PDO
pdo_mysql
pdo_sqlite

我的aws rds示例运行的是MySQL5.7.21。我也能够创建和运行实体的迁移，所以bin/console可以工作，但是symfony本身找不到合适的驱动程序。任何有助于这项工作的提示都非常感谢。谢谢！
下面是我的用户控制器

<?php

namespace App\Controller;

use App\Entity\User;
use Symfony\Component\Routing\Annotation\Route;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\HttpFoundation\Response;

class UserController extends Controller
{
    /**
     * @Route("/user", name="user")
     */
    public function index()
    {
        $entityManager = $this->getDoctrine()->getManager();

        $user = new User();
        $user->setName('Jay');
        $user->setUsername('testc');
        $user->setEmail('test@test.com');
        $user->setPassword(password_hash('testpassword', PASSWORD_DEFAULT));

        $entityManager->persist($user);

        $entityManager->flush();

        return new Response('Saved new user' . $user->getId());
    }
}