Get the balance of an account for a particular type of token.
    This is its credits minus its debits.
    Returns the current balance on success.
    Aborts on error, or if the balance is somehow negative.

def namedb_get_account_balance(account):
    """
    Get the balance of an account for a particular type of token.
    This is its credits minus its debits.
    Returns the current balance on success.
    Aborts on error, or if the balance is somehow negative.
    """
    # NOTE: this is only possible because Python does not overflow :P
    balance = account['credit_value'] - account['debit_value']
    if balance < 0:
        log.fatal("Balance of {} is {} (credits = {}, debits = {})".format(account['address'], balance, account['credit_value'], account['debit_value']))
        traceback.print_stack()
        os.abort()

    return balance