Insufficient permissions raise IO ValueError instead of PermissionError

[BorjaEst]

What is your issue?

I was getting the following error continuously when using xarray.open_mfdataset:

ValueError: did not find a match in any of xarray's currently installed IO backends ['netcdf4', 'h5netcdf', 'scipy', 'cfgrib', 'pydap', 'zarr']. Consider explicitly selecting one of the installed engines via the ``engine`` parameter, or installing additional IO dependencies

When the file file was indeed a netcdf4:

$ ncdump -k myfile.nc 
classic

I was running my script with the command inside a docker container, which uses a different user and group than myself. It seems the issue was on the permisions of the file as only my user had access:

$ ls -la
total 39M
-rw-r----- 1 borja borja 39M Mär 23 12:15 myfile.nc

Changing permission rights with chmod a+r myfile.nc solved the thing:

$ ls -la
total 39M
-rw-r--r-- 1 borja borja 39M Mär 23 12:15 myfile.nc

The permission thing is perfectly fine, it was my error, however, it would be nice that the command open_mfdataset (or related) would raise PermissionError when permissions are not sufficient.

[max-sixty]

Thanks, that is indeed confusing from xarray, we'd definitely take a PR for this.