multiindex + cftimeindex broken on pandas main

[dcherian]

What happened?

This test fails on pandas main branch

xarray/xarray/tests/test_cftimeindex.py

Lines 1191 to 1195 in 96e0ff7

	@requires_cftime
	def test_multiindex():
	index = xr.cftime_range("2001-01-01", periods=100, calendar="360_day")
	mindex = pd.MultiIndex.from_arrays([index])
	assert mindex.get_loc("2001-01") == slice(0, 30)

I will xfail this test but it would be good to fix it

cc @spencerkclark

[spencerkclark]

Thanks @dcherian—a bisect indicates pandas-dev/pandas#60118 led to this. I think the issue is that uniques is being cast to a plain Index instead of a CFTimeIndex. Previously the constructor of self was used, which would create a CFTimeIndex. I'll think about the best way to address this upstream.