Comment 0 for bug 1935818

[Description]
If PAM session fails to initialize completely, the session aborts as expected but GDM stays on VT1 and switches to a black screen.

[Test Plan]
1. In /etc/pam.d/gdm-password insert the line:
    session requisite pam_deny.so
After the line
    @include common-account
2. Login from GDM
3. Verify that:
  - The session fails to start
  - A black TTY is displayed
  - Active TTY is 1
4. Apply the patched version
5. Login from GDM
6. Verify the login fails but GDM is still displayed and an error message in printed under the password box.

[Where problem could occur]
* Cannot login at all with any user.

[Other info]

ProblemType: Bug
DistroRelease: Ubuntu 21.10
Package: gdm3 3.38.2.1-3ubuntu2
ProcVersionSignature: Ubuntu 5.11.0-20.21+21.10.1-generic 5.11.21
Uname: Linux 5.11.0-20-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu67
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Mon Jul 12 11:36:11 2021
InstallationDate: Installed on 2020-05-31 (407 days ago)
InstallationMedia: Ubuntu 20.10 "Groovy Gorilla" - Alpha amd64 (20200527)
SourcePackage: gdm3
UpgradeStatus: No upgrade log present (probably fresh install)