Return our appropriate resampler when grouping as well.

def get_resampler_for_grouping(groupby, rule, how=None, fill_method=None,
                               limit=None, kind=None, **kwargs):
    """
    Return our appropriate resampler when grouping as well.
    """

    # .resample uses 'on' similar to how .groupby uses 'key'
    kwargs['key'] = kwargs.pop('on', None)

    tg = TimeGrouper(freq=rule, **kwargs)
    resampler = tg._get_resampler(groupby.obj, kind=kind)
    r = resampler._get_resampler_for_grouping(groupby=groupby)
    return _maybe_process_deprecations(r,
                                       how=how,
                                       fill_method=fill_method,
                                       limit=limit)