add noxfile to run python linters

Currently, this only lints the noxfile itself and the issue labeler
script.
We can expand the noxfile to build docs and lint other new files in
hacking.

Relates: ansible#54

.isort.cfg

@@ -0,0 +1,2 @@
+[isort]
+profile = black

noxfile.py

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+import os
+from pathlib import Path
+
+import nox
+
+LINT_FILES = ("hacking/pr_labeler/label.py", "noxfile.py")
+PINNED = os.environ.get("PINNED", "true").lower() in {"1", "true"}
+nox.options.sessions = ("lint",)
+
+
+def install(session: nox.Session, *args, req: str, **kwargs):
+    if PINNED:
+        kwargs.setdefault("env", {})["PIP_CONSTRAINT"] = f"tests/{req}.txt"
+    session.install("-r", f"tests/{req}.in", *args, **kwargs)
+
+
+@nox.session
+def static(session: nox.Session):
+    """
+    Run static checkers
+    """
+    install(session, req="static")
+    session.run("ruff", *session.posargs, *LINT_FILES)
+
+
+@nox.session
+def formatters(session: nox.Session):
+    """
+    Reformat code
+    """
+    install(session, req="formatters")
+    session.run("isort", *session.posargs, *LINT_FILES)
+    session.run("black", *session.posargs, *LINT_FILES)
+
+
+@nox.session
+def formatters_check(session: nox.Session):
+    """
+    Check code formatting without making changes
+    """
+    install(session, req="formatters")
+    session.run("isort", "--check", *session.posargs, *LINT_FILES)
+    session.run("black", "--check", *session.posargs, *LINT_FILES)
+
+
+@nox.session
+def typing(session: nox.Session):
+    install(session, req="typing")
+    session.run("mypy", *session.posargs, *LINT_FILES)
+
+
+@nox.session
+def lint(session: nox.Session):
+    session.notify("static")
+    session.notify("formatters")
+
+
+requirements_files = list(
+    {path.name.replace(".in", "") for path in Path("tests").glob("*in")}
+    - {"constraints"}
+)
+
+
+@nox.session(name="pip-compile", python=["3.10"])
+@nox.parametrize(["req"], requirements_files, requirements_files)
+def pip_compile(session: nox.Session, req: str):
+    session.install("pip-tools")
+    # fmt: off
+    session.run(
+        "pip-compile",
+        "--resolver", "backtracking",
+        "--upgrade",
+        "--allow-unsafe",
+        "--quiet",
+        "--strip-extras",
+        "--output-file", f"tests/{req}.txt",
+        f"tests/{req}.in",
+    )
+    # fmt: on

tests/formatters.in

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+black
+isort

tests/formatters.txt

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+#
+# This file is autogenerated by pip-compile with Python 3.10
+# by the following command:
+#
+#    pip-compile --allow-unsafe --output-file=tests/formatters.txt --strip-extras tests/formatters.in
+#
+black==23.7.0
+    # via -r tests/formatters.in
+click==8.1.6
+    # via black
+isort==5.12.0
+    # via -r tests/formatters.in
+mypy-extensions==1.0.0
+    # via black
+packaging==23.1
+    # via black
+pathspec==0.11.2
+    # via black
+platformdirs==3.10.0
+    # via black
+tomli==2.0.1
+    # via black

tests/static.in

@@ -0,0 +1 @@
+ruff

tests/static.txt

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+#
+# This file is autogenerated by pip-compile with Python 3.10
+# by the following command:
+#
+#    pip-compile --allow-unsafe --output-file=tests/static.txt --strip-extras tests/static.in
+#
+ruff==0.0.284
+    # via -r tests/static.in

tests/typing.in

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+-r ../hacking/pr_labeler/requirements.txt
+mypy
+nox

tests/typing.txt

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+#
+# This file is autogenerated by pip-compile with Python 3.10
+# by the following command:
+#
+#    pip-compile --allow-unsafe --output-file=tests/typing.txt --strip-extras tests/typing.in
+#
+argcomplete==3.1.1
+    # via nox
+certifi==2023.7.22
+    # via requests
+cffi==1.15.1
+    # via
+    #   cryptography
+    #   pynacl
+charset-normalizer==3.2.0
+    # via requests
+click==8.1.6
+    # via typer
+codeowners==0.6.0
+    # via -r tests/../hacking/pr_labeler/requirements.txt
+colorlog==6.7.0
+    # via nox
+cryptography==41.0.3
+    # via pyjwt
+deprecated==1.2.14
+    # via pygithub
+distlib==0.3.7
+    # via virtualenv
+filelock==3.12.2
+    # via virtualenv
+idna==3.4
+    # via requests
+mypy==1.5.0
+    # via -r tests/typing.in
+mypy-extensions==1.0.0
+    # via mypy
+nox==2023.4.22
+    # via -r tests/typing.in
+packaging==23.1
+    # via nox
+platformdirs==3.10.0
+    # via virtualenv
+pycparser==2.21
+    # via cffi
+pygithub==1.59.1
+    # via -r tests/../hacking/pr_labeler/requirements.txt
+pyjwt==2.8.0
+    # via pygithub
+pynacl==1.5.0
+    # via pygithub
+requests==2.31.0
+    # via pygithub
+tomli==2.0.1
+    # via mypy
+typer==0.9.0
+    # via -r tests/../hacking/pr_labeler/requirements.txt
+typing-extensions==4.7.1
+    # via
+    #   codeowners
+    #   mypy
+    #   typer
+urllib3==2.0.4
+    # via requests
+virtualenv==20.24.2
+    # via nox
+wrapt==1.15.0
+    # via deprecated