Base CI setup

.flake8

+[flake8]
+max-line-length = 150
+exclude = .git,__pycache__
+ignore = E203,E501,W503

.gitlab-ci.yml

+stages:
+  - test
+  - build
+  - release
+
+lint:
+  image: python:3
+
+  cache:
+    paths:
+      - .cache/pip
+      - .cache/pre-commit
+
+  variables:
+    PIP_CACHE_DIR: "$CI_PROJECT_DIR/.cache/pip"
+    PRE_COMMIT_HOME: "$CI_PROJECT_DIR/.cache/pre-commit"
+
+  before_script:
+    - pip install pre-commit
+
+  script:
+    - pre-commit run -a

.isort.cfg

+[settings]
+# Compatible with black
+multi_line_output = 3
+include_trailing_comma = True
+force_grid_wrap = 0
+use_parentheses = True
+line_length = 88
+
+default_section=FIRSTPARTY
+known_first_party = arkindex,arkindex_common
+known_third_party =

.pre-commit-config.yaml

+repos:
+  - repo: https://github.com/asottile/seed-isort-config
+    rev: v2.2.0
+    hooks:
+      - id: seed-isort-config
+  - repo: https://github.com/pre-commit/mirrors-isort
+    rev: v4.3.21
+    hooks:
+      - id: isort
+  - repo: https://github.com/ambv/black
+    rev: stable
+    hooks:
+    - id: black
+  - repo: https://gitlab.com/pycqa/flake8
+    rev: 3.8.3
+    hooks:
+      - id: flake8
+        additional_dependencies:
+          - 'flake8-coding==1.3.1'
+          - 'flake8-copyright==0.2.2'
+          - 'flake8-debugger==3.1.0'
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.1.0
+    hooks:
+      - id: check-ast
+      - id: check-docstring-first
+      - id: check-executables-have-shebangs
+      - id: check-merge-conflict
+      - id: check-symlinks
+      - id: debug-statements
+      - id: trailing-whitespace
+      - id: check-yaml
+        args: [--allow-multiple-documents]
+      - id: mixed-line-ending
+      - id: name-tests-test
+        args: ['--django']
+      - id: check-json
+      - id: requirements-txt-fixer
+  - repo: https://github.com/codespell-project/codespell
+    rev: v1.17.1
+    hooks:
+      - id: codespell
+        args: ['--write-changes']
+  - repo: meta
+    hooks:
+      - id: check-useless-excludes
+
+default_language_version:
+  python: python3.7

hooks/pre-commit

+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# File generated by pre-commit: https://pre-commit.com
+# ID: 138fd403232d2ddd5efb44317e38bf03
+import os
+import sys
+
+# we try our best, but the shebang of this script is difficult to determine:
+# - macos doesn't ship with python3
+# - windows executables are almost always `python.exe`
+# therefore we continue to support python2 for this small script
+if sys.version_info < (3, 3):
+    from distutils.spawn import find_executable as which
+else:
+    from shutil import which
+
+# work around https://github.com/Homebrew/homebrew-core/issues/30445
+os.environ.pop("__PYVENV_LAUNCHER__", None)
+
+# start templated
+INSTALL_PYTHON = "/usr/bin/python3"
+ARGS = [
+    "hook-impl",
+    "--config=.pre-commit-config.yaml",
+    "--hook-type=pre-commit",
+    "--skip-on-missing-config",
+]
+# end templated
+ARGS.extend(("--hook-dir", os.path.realpath(os.path.dirname(__file__))))
+ARGS.append("--")
+ARGS.extend(sys.argv[1:])
+
+DONE = "`pre-commit` not found.  Did you forget to activate your virtualenv?"
+if os.access(INSTALL_PYTHON, os.X_OK):
+    CMD = [INSTALL_PYTHON, "-mpre_commit"]
+elif which("pre-commit"):
+    CMD = ["pre-commit"]
+else:
+    raise SystemExit(DONE)
+
+CMD.extend(ARGS)
+if sys.platform == "win32":  # https://bugs.python.org/issue19124
+    import subprocess
+
+    if sys.version_info < (3, 7):  # https://bugs.python.org/issue25942
+        raise SystemExit(subprocess.Popen(CMD).wait())
+    else:
+        raise SystemExit(subprocess.call(CMD))
+else:
+    os.execvp(CMD[0], CMD)