./bin/console c:cl

PHP Notice:  Undefined variable: exitCode in vendor/symfony/console/Application.php on line 886

In ConsoleTerminateEvent.php line 27:
                                                                                                                                                     
  Type error: Argument 4 passed to Symfony\Component\Console\Event\ConsoleTerminateEvent::__construct() must be of the type integer, null given, ca  
  lled in vendor/symfony/console/Application.php on line 886                                                                           
                                                                                                                                                     

cache:clear [--no-warmup] [--no-optional-warmers] [-h|--help] [-q|--quiet] [-v|vv|vvv|--verbose] [-V|--version] [--ansi] [--no-ansi] [-n|--no-interaction] [-e|--env ENV] [--no-debug] [--] <command>

composer create-project symfony/skeleton demo
cd demo
composer req mailer debug

APP_ENV=prod

monolog:
    handlers:
        mail:
            type:         fingers_crossed
            action_level: critical
            handler:      deduplicated
        deduplicated:
            type:    deduplication
            handler: swift
        swift:
            type:       swift_mailer
            from_email: '%env(EMAIL_SENDER)%'
            to_email:   '%env(EMAIL_RECIPIENT)%'
            subject:    'Error %env(ROUTER_HOST)%'
            level:      debug
            formatter:  monolog.formatter.html
            content_type: text/html

rm -rf var/cache/prod
./bin/console c:cl