message: Update deprecation notice to tf.contrib.ffmpeg
  This fix is related to 21549.
  The tf.contrib.ffmpeg will be removed from 2.0 and
  support for audio and video formats are not in
  tensorflow-io. This PR updates the deprecation
  notice so that users could be redirected to
  related project.
  This fix fixes 21549.
diff: @@ -29,8 +29,11 @@ from tensorflow.python.util.deprecation import deprecated
  _ffmpeg_so = loader.load_op_library(
  resource_loader.get_path_to_datafile('ffmpeg.so'))
  -
  -@deprecated('2018-09-04', 'This will be deleted and should not be used.')
  +@deprecated(
  + '2018-09-04',
  + 'tf.contrib.ffmpeg will be removed in 2.0, the support for video '
  + 'and audio will continue to be provided in tensorflow-io: '
  + 'https://github.com/tensorflow/io')
  def decode_audio(contents, file_format=None, samples_per_second=None,
  channel_count=None, stream=None):
  """Create an op that decodes the contents of an audio file.
  @@ -71,7 +74,11 @@ def decode_audio(contents, file_format=None, samples_per_second=None,
  ops.NotDifferentiable('DecodeAudio')
  -@deprecated('2018-09-04', 'This will be deleted and should not be used.')
  +@deprecated(
  + '2018-09-04',
  + 'tf.contrib.ffmpeg will be removed in 2.0, the support for video '
  + 'and audio will continue to be provided in tensorflow-io: '
  + 'https://github.com/tensorflow/io')
  def encode_audio(audio, file_format=None, samples_per_second=None):
  """Creates an op that encodes an audio file using sampled audio from a tensor.
  @@ -98,7 +105,11 @@ def encode_audio(audio, file_format=None, samples_per_second=None):
  ops.NotDifferentiable('EncodeAudio')
  -@deprecated('2018-09-04', 'This will be deleted and should not be used.')
  +@deprecated(
  + '2018-09-04',
  + 'tf.contrib.ffmpeg will be removed in 2.0, the support for video '
  + 'and audio will continue to be provided in tensorflow-io: '
  + 'https://github.com/tensorflow/io')
  def decode_video(contents):
  """Create an op that decodes the contents of a video file.
  