message: add deprecation notice.
diff: @@ -150,6 +150,16 @@ _raw_ops_doc = textwrap.dedent("""\n
  if LooseVersion(tf.__version__) < LooseVersion('2'):
  tf.raw_ops.__doc__ = _raw_ops_doc
  + tf.contrib.__doc__ = """
  + Contrib module containing volatile or experimental code.
  +
  + Warning: The `tf.contrib` module will not be included in TensorFlow 2.0. Many
  + of its submodules have been integrated into TensorFlow core, or spun-off into
  + other projects like [`tensorflow_io`](https://github.com/tensorflow/io), or
  + [`tensorflow_addons`](https://github.com/tensorflow/addons). For instructions
  + on how to upgrade see the
  + [Migration guide](https://www.tensorflow.org/beta/guide/migration_guide).
  + """
  else:
  tf.raw_ops.__doc__ += _raw_ops_doc
  