GNOME session fails to start on GPU nodes

[mjtko]

When launching a GNOME session on a GPU node, the VNC server logs show:

Xlib:  extension "GLX" missing on display ":1".
gnome-session-is-accelerated: No hardware 3D support.
Xlib:  extension "GLX" missing on display ":1".
gnome-session-check-accelerated: Helper exited with code 256
Xlib:  extension "GLX" missing on display ":1".
gnome-session-is-accelerated: No hardware 3D support.
Xlib:  extension "GLX" missing on display ":1".
gnome-session-check-accelerated: Helper exited with code 256

On connection to the session a grey "something went wrong" GNOME message is shown with an OK button. The session is non-functional.

[mjtko]

References:

TigerVNC/tigervnc#39 (comment)
https://groups.google.com/forum/#!topic/tigervnc-users/jbHetKZQLKY

[sierra-tango-echo]

Problem may have moved to a different one?

[alces@login1(sfn-pbs) ~]$ cat /etc/alces-imageware.yaml
:distro: centos
:distromajorversion: '7'
:baseimageversion: 'centos7-base-2.1'
:imageware: 'release/2016.4'
:buildtime: '2017-01-06_16-59'
:flightapplianceplatform: 'aws'
:flightappliancename: 'compute'
:flightapplianceversion: '2.3.0'
:clusterwareversion: 'release/1.7'

From session.log..

Fri Jan  6 17:32:58 2017
 vncext:      VNC extension running!
 vncext:      Listening for VNC connections on all interface(s), port 5901
 vncext:      created VNC server for screen 0
gnome-session-is-accelerated: No hardware 3D support.
gnome-session-check-accelerated: Helper exited with code 256

Fri Jan  6 17:33:15 2017
 Connections: accepted: 213.83.69.6::52003
 SConnection: Client needs protocol version 3.3
 VNCSConnST:  Server default pixel format depth 24 (32bpp) little-endian rgb888
 VNCSConnST:  Client pixel format depth 32 (32bpp) little-endian rgb max
              255,255,255 shift 16,8,0
gnome-session-is-accelerated: No hardware 3D support.
gnome-session-check-accelerated: Helper exited with code 256

** (process:16359): WARNING **: software acceleration check failed: Child process exited with code 1