安装配置openstack时，到keystone部分时，运行openstack service create --name keystone --description "OpenStack Identity" identity提示如下错误：
ERROR:openstack Internal ServerError(HTTP 500)
什么原因产生这种情况？配置错误吗？该如何处理呢？
查看 /var/log/keystone/keystone.conf，该文件里没有任何内容，
查看/var/log/httpd/keystone-error.log有如下内容：
2017-10-10 14:19:15.144225 mod_wsgi (pid=8576, process='keystone-admin', application=''): Loading WSGI script '/var/www/cgi-bin/keystone/admin'.
2017-10-10 14:19:15.851922 mod_wsgi (pid=8576): Target WSGI script '/var/www/cgi-bin/keystone/admin' cannot be loaded as Python module.
2017-10-10 14:19:15.851947 mod_wsgi (pid=8576): Exception occurred processing WSGI script '/var/www/cgi-bin/keystone/admin'.
2017-10-10 14:19:15.851968 Traceback (most recent call last):
2017-10-10 14:19:15.851981 File "/var/www/cgi-bin/keystone/admin", line 4, in
2017-10-10 14:19:15.852019 application = wsgi_server.initialize_application(name)
2017-10-10 14:19:15.852027 File "/usr/lib/python2.7/site-packages/keystone/server/wsgi.py", line 36, in initialize_application
2017-10-10 14:19:15.852057 common.configure()
2017-10-10 14:19:15.852063 File "/usr/lib/python2.7/site-packages/keystone/server/common.py", line 36, in configure
2017-10-10 14:19:15.852088 config.setup_logging()
2017-10-10 14:19:15.852097 File "/usr/lib/python2.7/site-packages/keystone/config.py", line 56, in setup_logging
2017-10-10 14:19:15.852127 log.setup(CONF, 'keystone')
2017-10-10 14:19:15.852133 File "/usr/lib/python2.7/site-packages/oslo_log/log.py", line 211, in setup
2017-10-10 14:19:15.852219 setup_logging_from_conf(conf, product_name, version)
2017-10-10 14:19:15.852227 File "/usr/lib/python2.7/site-packages/oslo_log/log.py", line 263, in _setup_logging_from_conf
2017-10-10 14:19:15.852238 filelog = logging.handlers.WatchedFileHandler(logpath)
2017-10-10 14:19:15.852244 File "/usr/lib64/python2.7/logging/handlers.py", line 392, in __init_
2017-10-10 14:19:15.852459 logging.FileHandler.__init__(self, filename, mode, encoding, delay)
2017-10-10 14:19:15.852469 File "/usr/lib64/python2.7/logging/__init__.py", line 902, in init
2017-10-10 14:19:15.852751 StreamHandler.__init__(self, self._open())
2017-10-10 14:19:15.852760 File "/usr/lib64/python2.7/logging/__init__.py", line 925, in _open
2017-10-10 14:19:15.852771 stream = open(self.baseFilename, self.mode)
2017-10-10 14:19:15.852784 IOError: [Errno 13] Permission denied: '/var/log/keystone/keystone.log'
