/usr/share/doc/python3-notmuch/changelog.Debian.gz is in python3-notmuch 0.21-3ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/python3-notmuch/../libnotmuch4/changelog.Debian.gz
/usr/share/doc/python3-notmuch/../libnotmuch4/changelog.Debian.gz