Unable to add application user in EAP 6.2.0

Issue

• Unable to add application user in EAP 6.2.0 .
• How to add user in EAP 6.2.0 ?
• While adding a user in EAP 6.2.0 , getting below error :

[user@user bin]$ ./add-user.sh 

What type of user do you wish to add? 
 a) Management User (mgmt-users.properties) 
 b) Application User (application-users.properties)
(a): b

Enter the details of the new user to add.
Using realm 'ApplicationRealm' as discovered from the existing property files.
Username : admin_user 

 * Error * 
JBAS015239: Only alpha/numeric usernames accepted.