Comment 6 for bug 1749728

from my auth.log file:

before modifying the terminal flag in gdebi.desktop

Jul 8 15:20:46 johndoe-Latitude-D630 polkitd(authority=local): Operator of unix-session:c2 FAILED to authenticate to gain authorization for action com.ubuntu.pkexec.gdebi.gtk for unix-process:998:23188 [/lib/systemd/systemd --user] (owned by unix-user:johndoe)

Jul 8 15:20:46 johndoe-Latitude-D630 pkexec[4230]: johndoe: Error executing command as another user: Request dismissed [USER=root] [TTY=unknown] [CWD=/home/johndoe/tmp] [COMMAND=/usr/bin/gdebi-gtk --non-interactive /home/johndoe/tmp/mozilla_johndoe0/ghex_3.18.3-3_amd64.deb]

after modifying the terminal flag in gdebi.desktop

Jul 8 15:35:26 johndoe-Latitude-D630 polkitd(authority=local): Operator of unix-session:c2 successfully authenticated as unix-user:johndoe to gain ONE-SHOT authorization for action com.ubuntu.pkexec.gdebi.gtk for unix-process:5533:234898 [/usr/lib/firefox/firefox] (owned by unix-user:johndoe)

Jul 8 15:35:26 johndoe-Latitude-D630 pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)

Jul 8 15:35:26 johndoe-Latitude-D630 pkexec[5699]: johndoe: Executing command [USER=root] [TTY=unknown] [CWD=/home/johndoe] [COMMAND=/usr/bin/gdebi-gtk --non-interactive /home/johndoe/tmp/mozilla_johndoe0/ghex_3.18.3-3_amd64.deb]