Read a gzipped netcdf file

and over here:

    if sys.version_info[:2] < (2, 7):
        with self.assertRaisesRegexp(ValueError, 'gzipped netCDF not supported'):
            open_example_dataset('example_1.nc.gz')
    else:
        ...

where `...` is what you currently have.

Might need to add a `import sys`, too.