To avoid this error, you can follow the bellow given steps.
You should check the keystone log-file. By default, the keystone logfile is located at “/var/log/keystone/keystone.log” and see what caused HTTP 500 error.
Check if you are referring to the right ‘OS_SERVICE_ENDPOINT‘ and OS_SERVICE_TOKEN.
#export OS_SERVICE_TOKEN= <valid_token>
You should also compare ‘OS_SERVICE_ENDPOINT‘ and ‘OS_SERVICE_TOKEN’ entries in ‘/etc/keystone/keystone.conf‘ file.