ERROR "CRITICAL glance [-] AttributeError: 'NoneType' object has no attribute 'drivername'" in /var/log/glance/api.log

How reproducible:

Steps to Reproduce:
1.Install the Ubuntu Server 12.04.4
2.Install the Keystone
3.Install the Glance
4.type "glance-manage db_sync" commands.

Actual results:
2014-04-14 10:40:37.697 15295 CRITICAL glance [-] AttributeError: 'NoneType'
object has no attribute 'drivername'

The installed version:

# dpkg -l |grep glance
ii glance 1:2014.1~rc1-0ubuntu1~cloud0
OpenStack Image Registry and Delivery Service - Daemons
ii glance-api 1:2014.1~rc1-0ubuntu1~cloud0
OpenStack Image Registry and Delivery Service - API
ii glance-common 1:2014.1~rc1-0ubuntu1~cloud0
OpenStack Image Registry and Delivery Service - Common
ii glance-registry 1:2014.1~rc1-0ubuntu1~cloud0
OpenStack Image Registry and Delivery Service - Registry
ii python-glance 1:2014.1~rc1-0ubuntu1~cloud0
OpenStack Image Registry and Delivery Service - Python library
ii python-glanceclient 1:0.12.0-0ubuntu1~cloud0 Client
library for Openstack glance server.

Workaround:

# cd /etc/glance
# mkdir bak
# mv *.ini *.conf *.json bak/
# cd
# wget https://github.com/openstack/glance/archive/master.zip
# unzip master.zip
# cp glance-master/etc/* /etc/glance
# chown glance.glance *
# ls -l /etc/glance/
total 76
drwxr-xr-x 2 glance glance 4096 Apr 14 13:46 bak
-rw-r--r-- 1 glance glance 24066 Apr 14 13:54 glance-api.conf
-rw-r--r-- 1 glance glance 2603 Apr 14 13:47 glance-api-paste.ini
-rw-r--r-- 1 glance glance 7210 Apr 14 13:47 glance-cache.conf
-rw-r--r-- 1 glance glance 6036 Apr 14 13:54 glance-registry.conf
-rw-r--r-- 1 glance glance 863 Apr 14 13:47 glance-registry-paste.ini
-rw-r--r-- 1 glance glance 1860 Apr 14 13:47 glance-scrubber.conf
-rw-r--r-- 1 glance glance 982 Apr 14 13:47 logging.cnf.sample
-rw-r--r-- 1 glance glance 611 Apr 14 13:47 policy.json
-rw-r--r-- 1 glance glance 1186 Apr 14 13:47
property-protections-policies.conf.sample
-rw-r--r-- 1 glance glance 1065 Apr 14 13:47
property-protections-roles.conf.sample
-rw-r--r-- 1 glance glance 1259 Apr 14 13:47 schema-image.json
# glance-manage db_sync