/usr/share/doc/libgtksourceviewmm-3.0-dev/changelog.Debian.gz is in libgtksourceviewmm-3.0-dev 3.2.0-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libgtksourceviewmm-3.0-dev/../libgtksourceviewmm-3.0-0/changelog.Debian.gz