The credit card model in payment/models.py uses a block cipher to encrypt the number before writing to the database. The cipher requires input to be a length that is a multiple of 8. Although most cc numbers are 16 long these days there are numbers that are not multiples of 8 long. In this case, the encryption object throws an unhandled exception from storeCC().
The attached patch pads the cc number to an 8 byte multiple before encryption, and strips the padding when decrypting.