upstart sessions needs to create upstart cache directory

I was testing 14.04 using XFCE and Xubuntu desktop sessions. After logging users in, they would only be presented with a desktop background and no running session. Their /tmp/.xdc_cache_$USER/upstart/dbus.log showed:

/proc/self/fd/9: 4: /proc/self/fd/9: cannot create /path/to/user/home/.cache/upstart/dbus-session: Directory nonexistent
/proc/self/fd/9: 4: /proc/self/fd/9: cannot create /path/to/user/home/.cache/upstart/dbus-session: Directory nonexistent
/proc/self/fd/9: 4: /proc/self/fd/9: cannot create /path/to/user/home/.cache/upstart/dbus-session: Directory nonexistent

I killed the user sessions, modified /usr/share/upstart/sessions/dbus.conf, and was then able to successfully login.

--- dbus.conf.orig 2014-01-13 14:01:11.000000000 -0800
+++ dbus.conf 2014-03-31 16:57:01.948724000 -0700
@@ -10,6 +10,7 @@
 pre-start script
     DBUS_SESSION_BUS_ADDRESS=unix:abstract=$(mktemp -u /tmp/dbus-XXXXXXXXXX)
     initctl set-env --global DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS
+ if [ ! -d $HOME/.cache/upstart ]; then mkdir -p $HOME/.cache/upstart; fi
     echo "DBUS_SESSION_BUS_ADDRESS=${DBUS_SESSION_BUS_ADDRESS}" >$HOME/.cache/upstart/dbus-session
 end script