Symfony version(s) affected: 4.3

Description
https://github.com/sebastianbergmann/phpunit/blob/master/ChangeLog-8.3.md
Since PHPUnit 8.3, PHPUnit\Util\ErrorHandler::handleError() is not available anymore.

DeprecationErrorHandler.php relied on this method in DeprecationErrorHandler::handleError().

How to reproduce
This error is triggered by executing is_array($env = @include dirname(__DIR__) . '/.env.local.php') in our bootstrap.php file when it is included by FiledLoader, when launching our tests with PHPUnit.