/usr/share/man/man8/dhclient3.8.gz is in isc-dhcp-client 4.1.ESV-R4-0ubuntu5.10.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man8/dhclient.8.gz
/usr/share/man/man8/dhclient.8.gz