def on_cleanup_error(function, path, excinfo):
                click.secho("warning: failed to remove file or directory: {}\n"
                            "please delete it manually.".format(path),
                            fg="red")
def winding_flux(pos, flux, ax=0):
    """plot flux vs position"""
    if ax == 0:
        ax = plt.gca()
    ax.set_title('Winding Flux / Vs')
    ax.grid(True)
    for p, f in zip(pos, flux):
        ax.plot(p, f)