Bug#725444: gnome-session: "Something has gone wrong."-dialog (fail whale) makes login impossible

[Patrick]

Package: gnome-session
Version: 3.4.2.1-4
Severity: important
Tags: upstream

Dear Maintainer,

gnome-session may have problems when starting required components, which results in showing the dreaded "fail whale" dialog, stating "Something has gone wrong" ant that you should log off and on again, with only a single "log off" botton available, and being always on top. Of course the problem would most times not vanish by itself. That means that after loggin on again, the situation repeats, rendering the account with that desktop settings unusable.

This is especially annoying for following reasons:
* No option to choose, like 
  - reporting a bug, 
  - trying something else or 
  - continue with some limitations.
* No information what went wrong: 
  - No program name. It was hard alone to find out which program that was startet after login generated the dialog, which makes bug reporting rather hard.
  - No information about which component failed. 
  - No information about how to solve the problem. 
  - No information about where to find diagnostic information.
* If no other account is configured and how to switch to a Linux console is unknown to the user or disabled, this leaves a installation dead-locked. This is exactly where users are deprieved of options, get frusrated and start to spread slander about Debian and Gnome.

What I would expect:
* A meaingful error message:
"The Gnome Session Manager experienced a critical failure:
A required component could not be started: <component name>.
You can try to log in with <Gnome failsafe session>.
Details about this error can be found in <error log file path>.
Please get help from your adminstrator or read more about this situation at
<URL to emergency login help at Debian or Gnome offline or online help>.
"
* An error log.
* A guide for what to do in this situation.

Where I encountered this problem:
I have two accounts at my machine, one which is usually used by me with Gnome Classic, and a second (other persons account) which is usually used with Gnome. After upgrading testing yesterday (2013-10-04), I could not login today. I'm not sure which service did not start; it's rather obscure... 

Really _very_ annoying. I found reports of this situation back from 2007. It was a little hard to find the cause because people do not understand the problem (how should they) and to rather drastic things like deleting/recreating the user directory (I did that before in desparation) or reinstalling the complete machine. I could not find proper bug reports, and I reckon the comes from the fact that the dialog does it's best to hide helpful information from the user.

I had a look at the source eventually, and it turned out that every part of information that is available about the problem is deliberately dumped on the way to the dialog.

One blogpost that helped me a lot was:
  http://who-t.blogspot.co.at/2013/01/getting-rid-of-gnome-oh-no-something.html

I would have set the severity higher, but bugreport requires a reference to a policy violation reference for that, and the Debian Policy has no "must" or "should" rules about useless error messages.

Regards

Patrick

-- System Information:
Debian Release: jessie/sid
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.10-3-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_AT.UTF-8, LC_CTYPE=de_AT.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages gnome-session depends on:
ii  gnome-session-bin      3.4.2.1-4
ii  gnome-session-common   3.4.2.1-4
ii  gnome-settings-daemon  3.4.2+git20121218.7c1322-6+b2
ii  gnome-shell            3.4.2-16

Versions of packages gnome-session recommends:
ii  gnome-power-manager     3.8.2-1
ii  gnome-session-fallback  3.4.2.1-4

Versions of packages gnome-session suggests:
ii  desktop-base      7.0.3
ii  gnome-keyring     3.8.2-2
ii  gnome-user-guide  3.8.2-1

-- no debconf information