I was having the same problem, but went for a different solution:
I noticed that if I created a new user the login of that user went fine. I assumed then the problem was in my user config.
So I made a backup of my home folder and removed my original user.
Then I created it again and login was successful. Of course I have lost all my configs, but the programs were still installed. Then I started to copy back folder by folder from my backup home to my new, clean, home.
I narrowed down the issue to the gnome extensions folder. As soon as I copied it back, the login loop happened again. I can't tell which extension was causing the issue, because I removed the extensions folder and reinstalled them using Chrome.
the folder location is: HOME/.local/share/gnome-shell/extensions
Hope this helps users that had this issue. It was quite painful to see a LTS block in that way.
Cheers
sudo apt-get -y autoremove && sudo apt-get -y cleanthe problem was solved. perhaps you can log in if u switch to another session with CTRL+F2 or try the recovery mode and run the command on that level -> see: https://askubuntu.com/questions/24006/how-do-i-reset-a-lost-administrative-password/24024#24024 – AlexOnLinux Jan 18 '19 at 14:13