This bug was fixed in the package hplip - 3.15.7-0ubuntu4
--------------- hplip (3.15.7-0ubuntu4) wily; urgency=low
* debian/local/scripts/hp-plugin-ubuntu: Use pkexec instead of gksu (LP: #1496980).
-- Till Kamppeter <email address hidden> Thu, 17 Sep 2015 21:24:00 -0300
This bug was fixed in the package hplip - 3.15.7-0ubuntu4
---------------
hplip (3.15.7-0ubuntu4) wily; urgency=low
* debian/ local/scripts/ hp-plugin- ubuntu: Use pkexec instead of
gksu (LP: #1496980).
-- Till Kamppeter <email address hidden> Thu, 17 Sep 2015 21:24:00 -0300