Comment 12 for bug 1587550

I had face same problem while upgrading from ubuntu 16.04 to 17.04.To make it even worst my laptop shutdowned. Im a dummy, knows nothing technicali panicked.Tried to boot again but got stuck in login loop. I can type password, but then shows a error message.Bammm back to login screen. I googled and found a way. This is not a expert opinion, so use with caution.I had to use this only because my system rebooted.

ctrl+alt+f3 to get into terminal screen

 give username which you gave while installing it first time
then password

i figured its easy to upgrade from terminal than finding a tailor made solution for my problem

sudo apt-get update

sudo apt-get upgrade

sudo apt-get dist-upgrade

ran into some errors followed instruction with the error.After long waiting rebooted using
reboot

This solved my problem, now my laptop run ubuntu 17.04
after login an error message showed saying gconf (i forgot the version) could not be installed.Other than that every thing looks normal.