Why am I seeing 'SERVER_DOWN info: Connection refused, errno 111, desc : Can't contact LDAP server' in tower.log?

Issue

• LDAP Integration with Ansible Tower is not successful. Seeing the following errors in tower.log :

 WARNING  django_auth_ldap Caught LDAPError while authenticating mwaite: SERVER_DOWN({'info': 'Connection refused', 'errno': 111, 'desc': "Can't contact LDAP server"},)
 WARNING  awx.api.views Login failed for user user1
 WARNING  awx.api.generics status 400 received by user AnonymousUser attempting to access /api/v2/authtoken/ from x.x.x.x
 DEBUG    awx.main.tasks Last scheduler run was: <>
 WARNING  django_auth_ldap Caught LDAPError while authenticating user1: SERVER_DOWN({'info': 'Connection refused', 'errno': 111, 'desc': "Can't contact LDAP server"},)
 WARNING  awx.api.views Login failed for user user1
 WARNING  awx.api.generics status 400 received by user AnonymousUser attempting to access /api/v2/authtoken/ from x.x.x.x