Solution : https://service.sap.com/sap/support/notes/1603306 (SAP Service marketplace login required)
Key words : 
prerequisites program error solution implement required correction instruction, function module /grcpi/gria_usr_create, terms access control 10, create user reason, symptom password, generating
Related Notes : 
       
| 1597166 | CUP : Password not getting generated for CUA child | 
| 1591123 | Master Note for SAP Access Control 10.0 - Support Pack 5 |