'do_setup should throw error if shares file does not exist.'

def test_setup_should_throw_error_if_shares_file_does_not_exist(self):

    drv = nfs.NfsDriver(configuration=self.configuration)
    mock_os_path_exists = self.mock_object(os.path, 'exists')
    mock_os_path_exists.return_value = False
    with self.assertRaisesRegex(exception.NfsException, "NFS    config    file.*doesn't    exist"):
        drv.do_setup(self.context)
    mock_os_path_exists.assert_has_calls([mock.call(self.configuration.nfs_shares_config)])
