A Constraint Violation error is from the LDAP endpoint when provisioning sends a request to create a user to the endpoint but it rejects the operation due to violate constraints placed on the attribute. The constraint can be one of size or content (string only, no binary).
To find out exactly what attribute causes the error, you would need to turn on the trace log on your endpoint and make sure you capture the log when you perform the create user activity. The following knowledge doc explains logging. Check the section on endpoint logging: