/usr/share/doc/bladerf-fpga-hostedx40/changelog.Debian.gz is in bladerf-fpga-hostedx40 0.2016.01~rc1-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/bladerf-fpga-hostedx40/../libbladerf1/changelog.Debian.gz