Python: pre-commit + black + isort + mypy

[danielcweeks]

Add code infra for python project including pre-commit, black, isort, mypy to enforce standards.

[cabhishek]

@danielcweeks I'll look into setting this up

[samredai]

Here's a suggestion for the tox.ini changes for black and isort! There's some conflict between flake8 and isort's opinions but adding I100 and I202 to flake8's ignore should get them in sync. This will also let us run tox -e format to reformat the source files accordingly before committing and pushing (maybe that's what the pre-commit hook can run?).

[testenv:format]
description = reformat all source code
basepython = python3
deps =
    black
    isort
    flake8
skip_install = true
commands =
    isort --recursive --project iceberg --profile black setup.py src tests
    black setup.py src tests
    flake8 setup.py src tests

[testenv:linters]
basepython = python3
skip_install = true
deps =
    .
    {[testenv:isort]deps}
    {[testenv:black]deps}
    {[testenv:flake8]deps}
    {[testenv:bandit]deps}
    {[testenv:mypy]deps}
commands =
    {[testenv:isort]deps}
    {[testenv:black]deps}
    {[testenv:flake8]commands}
    {[testenv:bandit]commands}
    {[testenv:mypy]commands}

[testenv:isort]
basepython = python3
skip_install = true
deps =
    isort
commands =
    isort --recursive --project iceberg --profile black --check-only setup.py src tests

[testenv:black]
basepython = python3
skip_install = true
deps =
    black
commands =
    black --check --diff src setup.py tests

[cabhishek]

@samredai Thanks, I opened a PR here.