[Bug 36177] gdm logins should fail if a sourced session script fails

[Gary Coady]

Public bug reported:
https://launchpad.net/malone/bugs/36177

Affects: gdm (Ubuntu)
       Severity: Normal
       Priority: (none set)
         Status: Unconfirmed

Description:
When /etc/gdm/Xsession sources various other scripts, logging in will
still succeed if a script returns a non-zero exit code. All other login
managers have the opposite behaviour - logging in fails - because
/etc/X11/Xsession includes "set -e".

This can cause failures to go unseen by developers, if they generally
use gdm during development (see Malone #35852 for an example).

I really just want all login managers to have the same behaviour here,
so if this bug is rejected, I'll go and hassle the xorg team ;-) But
"fail early" sounds like it's more appropriate, IMHO.