'return a seq of n ints or raise'

def __call__(self, s):

    if isinstance(s, six.string_types):
        s = [x.strip() for x in s.split(u',')]
        err_msg = _str_err_msg
    else:
        err_msg = _seq_err_msg
    if ((self.n is not None) and (len(s) != self.n)):
        raise ValueError(err_msg.format(n=self.n, num=len(s), s=s))
    try:
        return [int(val) for val in s]
    except ValueError:
        raise ValueError(u'Could    not    convert    all    entries    to    ints')
