Add `pre-commit` with `black`, `isort` and `flake8`.

.flake8

@@ -0,0 +1,5 @@
+[flake8]
+ignore = E203, E266, E501, W503, F403, F401, F841
+max-line-length = 89
+max-complexity = 10
+select = B,C,E,F,W,T4,B9

.pre-commit-config.yaml

@@ -0,0 +1,29 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+
+  - repo: https://github.com/ambv/black
+    rev: 22.10.0
+    hooks:
+      - id: black
+        language_version: python3.8
+
+  - repo: https://github.com/pycqa/isort
+    rev: 5.10.1
+    hooks:
+      - id: isort
+        args: ["--profile", "black"]
+
+  - repo: https://gitlab.com/pycqa/flake8
+    rev: 3.9.2
+    hooks:
+      - id: flake8
+        exclude: "setup.py"
+
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.3.0
+    hooks:
+      - id: trailing-whitespace
+      # - id: end-of-file-fixer
+      # - id: check-yaml
+      # - id: check-added-large-files

pyproject.toml

@@ -0,0 +1,20 @@
+[tool.black]
+py38 = true
+include = '\.pyi?$'
+exclude = '''
+/(
+    \.git
+  | \.hg
+  | \.mypy_cache
+  | \.tox
+  | \.venv
+  | _build
+  | buck-out
+  | build
+  | dist
+
+  # The following are specific to Black, you probably don't want those.
+  | blib2to3
+  | tests/data
+)/
+'''

requirements-test.txt

@@ -1,4 +1,5 @@
 codecov
 coverage
+pre-commit == 2.20.0
 psycopg2
 tox