Add fee to Block

[danpadev]

Issue #54

[buckyroberts]

This logic won't quite work since there could be multiple non-fee Txs. In this case the fee_list would have multiple None items but would still be valid.

txs = [
    {
        "amount": 12.5,
        "recipient": "484b3176c63d5f37d808404af1a12c4b9649cd6f6769f35bdf5a816133623fbc"
    },
    {
        "amount": 18.5,
        "recipient": "684b3176c63d5f37d808404af1a12c4b9649cd6f6769f35bdf5a816133623fbc"
    },
    {
        "amount": 1,
        "fee": 'BANK',
        "recipient": "5e12967707909e62b2bb2036c209085a784fabbc3deccefee70052b6181c8ed8"
    },
    {
        "amount": 4,
        "fee": 'PV',
        "recipient": "ad1f8845c6a1abb6011a2a434a079a087c460657aad54329a84b406dce8bf314"
    }
]

fee_list = [tx.get('fee', None) for tx in txs]
fee_set = set(fee_list)
error = bool(len(fee_list) != len(fee_set))

print(error)