Why are we getting an error `yum-config-manager command not found`?

Issue

• Why are we unable to add a 3rd party repository?
• Why are we not able to enable / disable the Red Hat repository?

Example :

[root@rhel ~]# yum-config-manager --add-repo <repository_url> 
-bash: yum-config-manager: command not found 

Or

[root@rhel ~]# yum-config-manager --enable=rhel-server-rhscl-7-rpms
-bash: yum-config-manager: command not found