Bug#179904: xfree86-common: No message to the user when xdm/kdm login fails

[Petter Reinholdtsen <pere@hungry.com>]

Package: xfree86-common
Version: 4.1.0-16

When the user tries to log in using kdm, and his home directory is
full, the user is thrown out to the login screen without any
explanation.  I believe the user should get some kind of error message
displayed on the screen when this happen, to avoid confused users and
a lot of work for the system administrators having to answer questions
from the confused users.

I've tracked the problem into /etc/X11/XSession, where the login will
fail if XSession is unable to create the ~/.xsession-errors file.
This problem is reported using the message() function, but this
function only prints a message to stderr, and do not display anything
on the X display.

I suggest changing message() to check if $DISPLAY is set, and in this
case both pop up a dialog with the message and print the message to
stderr.  Something like this:

  message () {
    # pretty-print messages of arbitrary length
    echo "$*" | fold -s -w ${COLUMNS:-80} >&2;
    if [ ! -z "$DISPLAY" ] ; then
       xmessage "$*"
    fi
  }

This would make it easier to detect why the login fails.