package lightdm 1.18.1-0ubuntu1 failed to install/upgrade: sub-processo script post-installation instalado retornou estado de saída de erro 1

[Weiller]

weiller@weiller-MS-7641:~$ lsb_release -rd
Description: Ubuntu 16.04.6 LTS
Release: 16.04

weiller@weiller-MS-7641:~$ sudo apt-cache policy lightdm
lightdm:
  Installed: 1.18.1-0ubuntu1
  Candidate: 1.18.3-0ubuntu1.1
  Version table:
     1.18.3-0ubuntu1.1 500
        500 http://br.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
 *** 1.18.1-0ubuntu1 500
        500 http://br.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
        100 /var/lib/dpkg/status

I expected it to update to the current version. But when I turn on the computer, I expect it to load and when it arrives the part that would be the appearance of the login screen, it simply does not start getting a black screen but nothing happens. For me to dribble this screen, I have to press the CTRL + ALT + F1, enter Terminal mode with my user and password to from there I enter with the command "Startx". When I start, it has been asking me for a password to reorto an error. I do not deny and report anyway. But this is making me intrigued because whenever I have to go into command mode (Terminal) to start the system and I use this way but I believe it is some previous update package because some updates came a couple of days ago and after these updates, LightDM started to give this problem. This has happened to me a few times but I have always reinstalled the system. But this time I decided to report the bug to a possible solution.
Just forgive me if the translation is not 100% because I write in Portuguese to translate with Google Translate and send it to you. I hope I can be helpful in reporting this error so that I can get a fix as soon as possible.
I know I have a current version in the repository. It has this 1.18 and has one in the unstable repository 1.28. But I already installed and with all dependencies but the problem has not been solved. If I knew to send an update log two days ago or three days ago, the modifications that were made, you would probably be able to solve the problem from there since it started from that update. I just do not update Xubuntu to version 18.04 because I'm afraid of appearing more bugs and as this version has a long support, I decided to keep on expiring and then, having better conditions, I do the Update.

I hope I have helped and anything I will be at your disposal. In the meantime I will use the system this way while I await a solution coming from you. Thank you very much.

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: lightdm 1.18.1-0ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-45.48~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-45-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
Date: Sat Feb 23 16:13:01 2019
ErrorMessage: sub-processo script post-installation instalado retornou estado de saída de erro 1
InstallationDate: Installed on 2019-02-06 (16 days ago)
InstallationMedia: Xubuntu 16.04.5 LTS "Xenial Xerus" - Release amd64 (20180731)
LightdmConfig:
 [Seat:*]
 autologin-guest=false
 autologin-user=weiller
 autologin-user-timeout=0
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.5
 apt 1.2.29ubuntu0.1
SourcePackage: lightdm
Title: package lightdm 1.18.1-0ubuntu1 failed to install/upgrade: sub-processo script post-installation instalado retornou estado de saída de erro 1
UpgradeStatus: No upgrade log present (probably fresh install)