FPrint shenanigans

Show a "Fingerprint authentication successful" message

Replace in the required /etc/pam.d file 

auth sufficient pam_fprintd.so

by 

auth [success=ok new_authtok_reqd=ok default=2] pam_fprintd.so
auth optional pam_echo.so file=/usr/share/pam/fingerprint_success_message.txt
auth sufficient pam_permit.so