Add nightly build installation code snippet to prototype feature tutorials

[hwangjeff]

Tutorial notebooks that leverage TorchAudio prototype features don't run as-is on Google Colab due to its runtime's not having nightly builds pre-installed. To make it easier for users to run said notebooks in Colab, this PR adds a code block that installs nightly Pytorch and TorchAudio builds as a comment that users can copy and run locally.

[mthrok]

This information is almost equivalent to what https://pytorch.org/get-started/locally/ says, yet it could become obsolete if release team should decide to change the URL.

Since the new information is very specific to Google Colab, how about raising this as error message when import torchaudio.prototypes fails?

Placing something like the following after the first import torchaudio;print(torchaudio.__version__)

try:
    import torchaudio.prototype.ctc_decoder
except ModuleNotFoundError:
    print(message)
    raise

[mthrok]

FYI: this is the full snippet for colab to run ASR inference;

!pip3 uninstall -y torch torchvision torchaudio
!pip3 install --pre torch torchaudio --extra-index-url https://download.pytorch.org/whl/nightly/cpu
!pip3 install sentencepiece
!add-apt-repository -y ppa:savoury1/ffmpeg4
!apt-get -qq install -y ffmpeg

[hwangjeff]

updated

[mthrok]

I just realized that tutorials with RNN-T bundle, (online_asr_tutorial.py and device_asr.py) require sentencepiece as well. Could you add that to the comment as well?

[facebook-github-bot]

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[mthrok]

Looks good. Thanks!

[github-actions]

Hey @hwangjeff.
You merged this PR, but labels were not properly added. Please add a primary and secondary label (See https://github.com/pytorch/audio/blob/main/.github/process_commit.py)