chore: add flake8 pre-commit hook

Part-of: <https://dev.funkwhale.audio/funkwhale/funkwhale/-/merge_requests/2178>

.flake8

@@ -0,0 +1,11 @@
+# Use .flake8 file until pyproject.toml is supported
+# See https://github.com/PyCQA/flake8/issues/234
+[flake8]
+max-line-length = 120
+extend-exclude =
+    */migrations/*
+extend-ignore =
+    F405
+    W503
+    E203
+    E741

.gitlab-ci.yml

@@ -166,25 +166,6 @@ black:
       changes:
         - api/**/*
 
-flake8:
-  interruptible: true
-  image: python:3.7
-  stage: lint
-  variables:
-    GIT_STRATEGY: fetch
-  before_script:
-    - pip install 'flake8<3.7'
-  script:
-    - flake8 -v api
-  cache:
-    key: "$CI_PROJECT_ID__flake8_pip_cache"
-    paths:
-      - "$PIP_CACHE_DIR"
-  rules:
-    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
-      changes:
-        - api/**/*
-
 eslint:
   interruptible: true
   image: node:18-alpine

.pre-commit-config.yaml

@@ -23,3 +23,8 @@ repos:
         exclude: ^(docs/locales/.*/LC_MESSAGES)
       - id: mixed-line-ending
       - id: trailing-whitespace
+
+  - repo: https://github.com/pycqa/flake8
+    rev: 5.0.4
+    hooks:
+      - id: flake8

api/setup.cfg

@@ -1,8 +1,3 @@
-[flake8]
-max-line-length = 120
-exclude = .tox,.git,*/migrations/*,*/static/CACHE/*,docs,node_modules,tests/data,tests/music/conftest.py
-ignore = F405,W503,E203,E741
-
 [isort]
 skip_glob = .tox,.git,*/migrations/*,*/static/CACHE/*,docs,node_modules