There is no longer support for 8 bit color depth in TigerVNC (see:
https://github.com/TigerVNC/tigervnc/commit/e86d8720ba1e79b486ca29a5c2b27fa25811e6a2);
using it causes a fatal error.

Submitted upstream at: https://github.com/canonical/lightdm/pull/265.

diff --git a/data/lightdm.conf b/data/lightdm.conf
index 0df38429..60e3e8b4 100644
--- a/data/lightdm.conf
+++ b/data/lightdm.conf
@@ -160,4 +160,4 @@
 #listen-address=
 #width=1024
 #height=768
-#depth=8
+#depth=24
diff --git a/src/x-server-xvnc.c b/src/x-server-xvnc.c
index 68340d53..27ca4454 100644
--- a/src/x-server-xvnc.c
+++ b/src/x-server-xvnc.c
@@ -127,7 +127,7 @@ x_server_xvnc_init (XServerXVNC *server)
     XServerXVNCPrivate *priv = x_server_xvnc_get_instance_private (server);
     priv->width = 1024;
     priv->height = 768;
-    priv->depth = 8;
+    priv->depth = 24;
 }
 
 static void
diff --git a/tests/scripts/vnc-command.conf b/tests/scripts/vnc-command.conf
index 0f1e25fd..335956d9 100644
--- a/tests/scripts/vnc-command.conf
+++ b/tests/scripts/vnc-command.conf
@@ -19,7 +19,7 @@ command=Xvnc -option
 #?VNC-CLIENT CONNECT
 
 # Xvnc server starts
-#?XVNC-0 START GEOMETRY=1024x768 DEPTH=8 OPTION=TRUE
+#?XVNC-0 START GEOMETRY=1024x768 DEPTH=24 OPTION=TRUE
 
 # Daemon connects when X server is ready
 #?*XVNC-0 INDICATE-READY
diff --git a/tests/scripts/vnc-guest.conf b/tests/scripts/vnc-guest.conf
index 431bb244..ce2b97db 100644
--- a/tests/scripts/vnc-guest.conf
+++ b/tests/scripts/vnc-guest.conf
@@ -21,7 +21,7 @@ user-session=default
 #?VNC-CLIENT CONNECT
 
 # Xvnc server starts
-#?XVNC-0 START GEOMETRY=1024x768 DEPTH=8 OPTION=FALSE
+#?XVNC-0 START GEOMETRY=1024x768 DEPTH=24 OPTION=FALSE
 
 # Daemon connects when X server is ready
 #?*XVNC-0 INDICATE-READY
diff --git a/tests/scripts/vnc-login.conf b/tests/scripts/vnc-login.conf
index cdfe17b8..f0d65b7f 100644
--- a/tests/scripts/vnc-login.conf
+++ b/tests/scripts/vnc-login.conf
@@ -21,7 +21,7 @@ user-session=default
 #?VNC-CLIENT CONNECT
 
 # Xvnc server starts
-#?XVNC-0 START GEOMETRY=1024x768 DEPTH=8 OPTION=FALSE
+#?XVNC-0 START GEOMETRY=1024x768 DEPTH=24 OPTION=FALSE
 
 # Daemon connects when X server is ready
 #?*XVNC-0 INDICATE-READY
diff --git a/tests/scripts/vnc-open-file-descriptors.conf b/tests/scripts/vnc-open-file-descriptors.conf
index 753c84dd..e5d35730 100644
--- a/tests/scripts/vnc-open-file-descriptors.conf
+++ b/tests/scripts/vnc-open-file-descriptors.conf
@@ -21,7 +21,7 @@ user-session=default
 #?VNC-CLIENT CONNECT
 
 # Xvnc server starts
-#?XVNC-0 START GEOMETRY=1024x768 DEPTH=8 OPTION=FALSE
+#?XVNC-0 START GEOMETRY=1024x768 DEPTH=24 OPTION=FALSE
 
 # Daemon connects when X server is ready
 #?*XVNC-0 INDICATE-READY
dad2a5c62'>discovery: Recurse into directories pointed to by a symlink.</a><span class='msg-avail'>...<span class='msg-tooltip'>Reported by Christopher Baines &lt;mail@cbaines.net&gt;
and Alex Kost &lt;alezost@gmail.com&gt;
at &lt;https://lists.gnu.org/archive/html/guix-devel/2017-06/msg00290.html&gt;.

* guix/discovery.scm (scheme-files): When ENTRY is a symlink that
doesn't end in '.scm', call 'stat' and recurse if it points to a
directory.
* tests/discovery.scm ("scheme-modules recurses in symlinks to
directories"): New test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-06-18 00:14:07 +0200'>2017-06-18</span></td><td><a href='/guix/commit/tests/discovery.scm?id=d46c4423f46278bd2f96770ceb0667431414349e'>discovery: 'scheme-files' returns '() for a non-accessible directory.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes a regression introduced in
d27cc3bfaafe6b5b0831e88afb1c46311d382a0b.

Reported by Ricardo Wurmus &lt;rekado@elephly.net&gt;.

* guix/discovery.scm (scheme-files): Catch 'scandir*' system errors.
Return '() and optionally raise a warning upon 'system-error'.
* tests/discovery.scm ("scheme-modules, non-existent directory"): New
test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-05-03 23:50:15 +0200'>2017-05-03</span></td><td><a href='/guix/commit/tests/discovery.scm?id=cd903ef7871170d3c4eced45418459d293ef48a7'>Add (guix discovery).</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/discovery.scm, tests/discovery.scm: New files.
* gnu/packages.scm (scheme-files, file-name-&gt;module-name)
(scheme-modules, all-package-modules): Remove.
(fold-packages): Rewrite in terms of 'fold-module-public-variables'.
* gnu/tests.scm: Use (guix discovery).
* Makefile.am (MODULES): Add guix/discovery.scm.
(SCM_TESTS): Add tests/discovery.scm.
</span></span></td><td>Ludovic Courtès</td></tr>