remove pytest command line argument that raises errors when warnings are issued
remove pytest command line argument that raises errors when warnings are issued

jhamman/xarray,pydata/xarray,jhamman/xray,xray/xray,markelg/xray,jcmgray/xarray,rabernat/xray,markelg/xray,pydata/xarray,pydata/xarray,chunweiyuan/xarray,markelg/xray,shoyer/xarray,jhamman/xarray,shoyer/xarray,rabernat/xray,jhamman/xarray,shoyer/xray