Trap and reports the reason for a failed card

This change traps and reports the reason for a failed card. In test mode using the following details will trigger this:

credit card number: 5105105105105100
the CVV is any 3-digit number you can choose on your own.
expiry: 03/2020

note: without this change an error will be thrown for invalid card details. This fix has not been battle tested :)