hello deepak, the error is because you need to source admin-credentials

for the first user better you set environmental variables like OS_SERVICE_TOKEN and OS_SERVICE_ENDPOINT by the following command.

openssl rand -hex 10  (this will produce a 10 digit key copy it) then type
export OS_SERVICE_TOKEN=10 digit key   
export OS_SERVICE_ENDPOINT=http://controller:35357/v2.0

if this works properly then for second time onwards you have to create admin-openrc.sh filef first. then execute the following command

keystone --os-username=admin --os-password=ADMIN_PASS --os-auth-url=http://controller:35357/v2.0 token-get

this returns a token with name and id generated randomly (don't panic output would be bigger than your screen) after that run the below command

keystone --os-username=admin --os-password=ADMIN_PASS --os-tenant-name=admin --os-auth-url=http://controller:35357/v2.0 \
token-get

now copy the credentials to your admin-openrc file

export OS_USERNAME=admin
export OS_PASSWORD=ADMIN_PASS
export OS_TENANT_NAME=admin
export OS_AUTH_URL=http://controller:35357/v2.0

just remember where you create this file its better to create it in /etc/keystone then source it by the command

source admin-openrc.sh