$ locate unity-newrelease-checker
/etc/xdg/autostart/unity-newrelease-checker.desktop
$ cat /etc/xdg/autostart/unity-newrelease-checker.desktop
[Desktop Entry]
Type=Application
Name=Unity New RC check
Comment=Check if a New RC from the unity ppa is available to display the info
Icon=checkbox
Exec=/usr/share/checkbox-unity/unity-newrelease-checker
OnlyShowIn=Unity;
X-GNOME-Autostart-Delay=30
X-GNOME-Autostart-Phase=Application
X-Ubuntu-Gettext-Domain=checkbox-unity
$cat /usr/share/checkbox-unity/unity-newrelease-checker
cat: /usr/share/checkbox-unity/unity-newrelease-checker: No such file or directory

As consecuence, I get on .xsession-errors

gnome-session[3656]: WARNING: Could not launch application 'unity-newrelease-checker.desktop':