/usr/share/php/Symfony/Component/Validator/Mapping/Loader/ is in php-symfony-validator 3.4.6+dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/AbstractLoader.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/AnnotationLoader.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/FileLoader.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/FilesLoader.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/LoaderChain.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/LoaderInterface.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/StaticMethodLoader.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/XmlFileLoader.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/XmlFilesLoader.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/YamlFileLoader.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/YamlFilesLoader.php
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/schema/
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/schema/dic/
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/schema/dic/constraint-mapping/
/usr/share/php/Symfony/Component/Validator/Mapping/Loader/schema/dic/constraint-mapping/constraint-mapping-1.0.xsd