Spectrum.py polyfit

in spectrum.py poly_fit(), l1031 introduced a repeat of

     err = d - np.polynomial.polynomial.polyval(w, p)

was introduced:

    if maxiter > 0:
        err = d - np.polynomial.polynomial.polyval(w, p)
        sig = np.std(err)
        n_p = len(d)
        for it in range(maxiter):
            err = d - np.polynomial.polynomial.polyval(w, p)
            ind = np.where((err >= nsig[0] * sig) &
                           (np.abs(err) <= nsig[1] * sig))
            if len(ind[0]) == n_p:
                break
            if len(ind[0]) <= deg + 1:
                raise ValueError('Too few points to perform '
                                 'polynomial fit')
            if vec_weight is not None:
                vec_weight = vec_weight[ind]
            p = np.polynomial.polynomial.polyfit(w[ind], d[ind],
                                                 deg, w=vec_weight)
            err = d[ind] - np.polynomial.polynomial.polyval(w[ind], p)
            sig = np.std(err)
            n_p = len(ind[0])

but caused a bug.

while using pyplatefit.