/usr/share/doc/php-symfony-polyfill-php56/changelog.Debian.gz is in php-symfony-polyfill-php56 1.6.0-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/php-symfony-polyfill-php56/../php-symfony-polyfill-util/changelog.Debian.gz