class_docstr: OSS Filesystem Tests
code: def test_file_read_bad_mode(self):
      file_path = file_io.join(self._base_dir, "temp_file")
      with gfile.Open(file_path, mode="wb") as f:
          f.write("testing")
      self.assertTrue(file_io.file_exists(file_path))
      with self.assertRaises(errors.PermissionDeniedError):
          gfile.Open(file_path, mode="w").read()
  
imports: import os
  import unittest
  from tensorflow.python.framework import errors
  from tensorflow.python.lib.io import file_io
  from tensorflow.python.platform import test
  from tensorflow.python.platform import gfile
  import tensorflow
  import tensorflow_io
label_desc: Use image node_id 14 for calling the OSSFSTest obj's underlying member method code with example usage: obj.test_file_read_bad_mode() without return types