Calculate the imei check byte.

def imeicsum(text):
    '''
    Calculate the imei check byte.
    '''
    digs = []
    for i in range(14):

        v = int(text[i])
        if i % 2:
            v *= 2

        [digs.append(int(x)) for x in str(v)]

    chek = 0
    valu = sum(digs)
    remd = valu % 10
    if remd != 0:
        chek = 10 - remd

    return str(chek)