'Extend an existing volume\'s size.'

def extend_volume(self, volume, new_size):

    data = {'vol-size': (six.text_type(new_size) + 'g')}
    try:
        self.client.req('volumes', 'PUT', data, name=volume['id'])
    except exception.NotFound:
        msg = _("can't    find    the    volume    to    extend")
        raise exception.VolumeDriverException(message=msg)
