The keystone CLI is deprecated in favor of python-openstackclient.

[root@controller ~]# keystone user-list
/usr/lib/python2.7/site-packages/keystoneclient/shell.py:64: DeprecationWarning: The keystone CLI is deprecated in favor of python-openstackclient. For a Python library, continue using python-keystoneclient.
  'python-keystoneclient.', DeprecationWarning)
Expecting an auth URL via either --os-auth-url or env[OS_AUTH_URL]
[root@controller ~]# 

猜测：
很可能是环境中已经将这个命令给放弃了，现在新的命令是openstakc user list
可以查询OpenStack的用户列表。