Failing test by dask==0.18.2

[fujiisoup]

Tests are failing, which is caused by new release of dask==0.18.2.
xref: dask/dask#3822

[shoyer]

This has resurfaced... I marked the test as xfail on 0.18.2, but didn't verify that my fix for the dask issue actually fixed this :(

[shoyer]

Actually, it turns up for another dtype with the same test. Details to follow in a new dask issue.