Addition of black-nb to CI check to avoid inconsistency in indentation

[paniash]

Fixes #3976 and added quotations around variables. See here.

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[google-cla]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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[paniash]

@googlebot I signed it!

[vtomole]

@paniash Thanks for opening this. Why isn't the Notebook Formating check failing?

[paniash]

@vtomole Hmmm.... I'll have to check what's going wrong. Sorry about that. I'll do it over the weekend.

[vtomole]

@paniash The right test is failing but probably not for the right reason. The log says:

check/nbformat: line 51: [: missing `]'
check/nbformat: line 51: -z: command not found

[paniash]

@vtomole Hi! Thanks for letting me know. I've fixed it and looks good from my side. Let me know if it's alright. :-)

[vtomole]

I get

./check/nbformat: line 55: python3 -m tensorflow_docs.tools.nbfmt --indent=1: command not found

When I call ./check/nbformat --apply. This is at the end, after all the notebooks have been formatted.

[balopat]

I ran this locally and had a bunch of issues:

check/nbformat: line 51: [: missing `]'
check/nbformat: line 51: -z: command not found
reformatted docs/qcvv/xeb_coherent_noise.ipynb
    14 cells reformatted, 2 cells left unchanged, 1 cell failed to reformat.
reformatted docs/circuits.ipynb
    5 cells reformatted, 12 cells left unchanged, 1 cell failed to reformat.
reformatted docs/protocols.ipynb
    4 cells reformatted, 5 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/quantum_walks.ipynb
    9 cells reformatted, 4 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/heatmaps.ipynb
    2 cells reformatted, 1 cell left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/google/floquet.ipynb
    16 cells reformatted, 17 cells left unchanged, 1 cell failed to reformat.
reformatted docs/qudits.ipynb
    2 cells reformatted, 1 cell failed to reformat.
reformatted docs/qcvv/isolated_xeb.ipynb
    10 cells reformatted, 4 cells left unchanged, 1 cell failed to reformat.
error: cannot format docs/custom_gates.ipynb: INTERNAL ERROR: Black produced different code on the second pass of the formatter.
reformatted docs/tutorials/educators/ion_device.ipynb
    3 cells reformatted, 4 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/qaoa.ipynb
    13 cells reformatted, 1 cell left unchanged, 1 cell failed to reformat.
reformatted docs/google/concepts.ipynb
    2 cells reformatted, 1 cell failed to reformat.
reformatted docs/tutorials/educators/qaoa_ising.ipynb
    13 cells reformatted, 10 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/hidden_linear_function.ipynb
    8 cells reformatted, 2 cells left unchanged, 1 cell failed to reformat.
reformatted docs/operators_and_observables.ipynb
    2 cells reformatted, 27 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/google/colab.ipynb
    4 cells reformatted, 1 cell failed to reformat.
reformatted docs/transform.ipynb
    3 cells reformatted, 1 cell failed to reformat.
error: cannot format docs/tutorials/educators/intro.ipynb: INTERNAL ERROR: Black produced different code on the second pass of the formatter.
reformatted docs/qubits.ipynb
    1 cell reformatted, 1 cell left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/basics.ipynb
    9 cells reformatted, 6 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/aqt/getting_started.ipynb
    6 cells reformatted, 1 cell left unchanged, 1 cell failed to reformat.
reformatted docs/simulation.ipynb
    12 cells reformatted, 4 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/google/echoes.ipynb
    7 cells reformatted, 7 cells left unchanged, 1 cell failed to reformat.
reformatted docs/noise.ipynb
    9 cells reformatted, 14 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/ionq/getting_started.ipynb
    6 cells reformatted, 3 cells left unchanged, 1 cell failed to reformat.
reformatted docs/interop.ipynb
    5 cells reformatted, 1 cell left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/google/visualizing_calibration_metrics.ipynb
    18 cells reformatted, 1 cell left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/google/reservations.ipynb
    10 cells reformatted, 1 cell failed to reformat.
reformatted docs/tutorials/shor.ipynb
    11 cells reformatted, 10 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/pasqal/getting_started.ipynb
    6 cells reformatted, 6 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/google/start.ipynb
    7 cells reformatted, 2 cells left unchanged, 1 cell failed to reformat.
reformatted docs/gates.ipynb
    2 cells reformatted, 1 cell failed to reformat.
reformatted docs/tutorials/educators/textbook_algorithms.ipynb
    12 cells reformatted, 20 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/rabi_oscillations.ipynb
    13 cells reformatted, 2 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/educators/chemistry.ipynb
    18 cells reformatted, 6 cells left unchanged, 1 cell failed to reformat.
reformatted docs/_template.ipynb
    1 cell reformatted, 1 cell failed to reformat.
reformatted docs/qcvv/parallel_xeb.ipynb
    13 cells reformatted, 5 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/educators/neutral_atom.ipynb
    7 cells reformatted, 14 cells left unchanged, 1 cell failed to reformat.
reformatted docs/tutorials/variational_algorithm.ipynb
    12 cells reformatted, 3 cells left unchanged, 1 cell failed to reformat.
reformatted docs/qcvv/xeb_theory.ipynb
    10 cells reformatted, 2 cells left unchanged, 1 cell failed to reformat.
All done! ✨ 🍰 ✨
38 files reformatted, 2 files failed to reformat.
check/nbformat: line 55: python3 -m tensorflow_docs.tools.nbfmt --indent=1: command not found

Thanks @paniash for working on this, though I'm not convinced yet that this is a good direction.

I think the first big question is: does black-nb and tf-docs.nbfmt collide with each other or not? By collide I mean that do they agree on the same formatting? If they don't agree, then we could never have a well formatted notebook!

Second main concern is that we need the tf_docs nbformat to be the last formatter, otherwise the site publishing will fail - they do run internally this nbfmt to ensure things are well formatted.

Third concern is that you haven't seem to have tested the user friendliness of the output in these cases:

1. check/nbformat - should report all the unformatted notebooks by path. The script currently does not do that for the black unformatted notebooks.

The following notebooks require formatting.

Notebooks are not formatted. Please run 'check/nbformat --apply'

2. check/nbformat --apply - there are a ton of issues where it fails on cells, is that okay to ignore or not? Does it report a non zero exit status? If it does, the Github Actions job will fail?

[vtomole]

Hey @paniash, Are you planning on opening a new PR with the changes?