Fix test failures with numpy=1.16 (#2675)
Fix test failures with numpy=1.16 (#2675)

Fixes https://github.com/pydata/xarray/issues/2673

Note that these were only test failures, not a real bug.
jhamman/xarray,markelg/xray,chunweiyuan/xarray,xray/xray,shoyer/xarray,jhamman/xray,shoyer/xarray,jhamman/xarray,markelg/xray,shoyer/xray,pydata/xarray,jhamman/xarray,markelg/xray,pydata/xarray,pydata/xarray