When install module or upgrade facet :
problem :
endor/symfony/symfony/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php on line 1403
Solution :
update ligne 1403 in
comment by add //
fichier /vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
// throw new RuntimeException(sprintf('Cannot dump definition because of invalid class name (%s)', $class ?: 'n/a'));