def run_ffitch(distfile, outtreefile, intreefile=None, **kwargs):
    """
    Infer tree branch lengths using ffitch in EMBOSS PHYLIP
    """
    cl = FfitchCommandline(datafile=distfile, outtreefile=outtreefile, \
            intreefile=intreefile, **kwargs)
    r, e = cl.run()

    if e:
        print("***ffitch could not run", file=sys.stderr)
        return None
    else:
        print("ffitch:", cl, file=sys.stderr)
        return outtreefile