remove libraries by GUI.

def gui():
    """remove libraries by GUI."""

    sel = psidialogs.multi_choice(libraries(),
                                  'select libraries to remove from %s!' % libraries_dir(),
                                  title='remove boards')
    print('%s selected' % sel)

    if sel:
        if psidialogs.ask_yes_no('Do you really want to remove selected libraries?\n' + '\n'.join(sel)):
            for x in sel:
                remove_lib(x)
                print('%s was removed' % x)