ERROR when entering OpenStack commands, "The request you have made requires authentication."

Issue

There can be different scenarios in which we get this error.

• For any OpenStack command we get ERROR (Unauthorized): The request you have made requires authentication. (HTTP 401)

[root@localhost ~(keystone_admin)]# nova list
ERROR (Unauthorized): The request you have made requires authentication. (HTTP 401) (Request-ID: req-6552e53f-168c-415e-8fc6-27b28a12739a)


[root@localhost ~(keystone_admin)]# grep -r "6552e53f-168c-415e-8fc6-27b28a12739" /var/log/
/var/log/keystone/keystone.log:2016-05-10 14:38:30.881 99332 INFO keystone.common.wsgi [req-6552e53f-168c-415e-8fc6-27b28a12739a - - - - -] POST http://172.23.89.44:5000/v2.0/tokens
/var/log/keystone/keystone.log:2016-05-10 14:38:30.896 99332 WARNING keystone.common.wsgi [req-6552e53f-168c-415e-8fc6-27b28a12739a - - - - -] Authorization failed. The request you have made requires authentication. from 172.23.89.44
/var/log/httpd/keystone_wsgi_main_error.log:[Tue May 10 14:38:30.882095 2016] [:error] [pid 99332] 2016-05-10 14:38:30.881 99332 INFO keystone.common.wsgi [req-6552e53f-168c-415e-8fc6-27b28a12739a - - - - -] POST http://172.23.89.44:5000/v2.0/tokens
/var/log/httpd/keystone_wsgi_main_error.log:[Tue May 10 14:38:30.897398 2016] [:error] [pid 99332] 2016-05-10 14:38:30.896 99332 WARNING keystone.common.wsgi [req-6552e53f-168c-415e-8fc6-27b28a12739a - - - - -] Authorization failed. The request you have made requires authentication. from 172.23.89.44 

• Launch of instance failed with ERROR 'Unauthorized: The request you have made requires authentication.' in '/var/log/nova/nova-compute.log'.

[root@localhost ~(keystone_admin)]# tail -f /var/log/nova/nova-compute.log
...
...
2017-07-05 19:36:29.838 8569 ERROR nova.compute.manager [req-0f48caf4-90f9-4ba9-b05a-9c64ed935d0b fb26863c826744178463272901158271 74656dda66bc4a40b6d0add2df3d9eb8 - - -] Instance failed network setup after 1 attempt(s)
2017-07-05 19:36:29.838 8569 ERROR nova.compute.manager Traceback (most recent call last):
2017-07-05 19:36:29.838 8569 ERROR nova.compute.manager   File "/usr/lib/python2.7/site-packages/nova/compute/manager.py", line 1401, in _allocate_network_async
2017-07-05 19:36:29.838 8569 ERROR nova.compute.manager     bind_host_id=bind_host_id)
...
...
2017-07-05 19:36:29.846 8569 ERROR nova.compute.manager [instance: c42c8d2f-22ad-4f21-9c36-61ea81f0dd81] Unauthorized: The request you have made requires authentication. (HTTP 401) (Request-ID: req-825422a7-68ca-4d0d-9d87-d68a9af8e5ce)