Add pre-commit config for flake8 (#8068)

This makes it easier to lint your own work with `pre-commit`, but doesn't change the CI config by adding this to the pre-commit.ci skip list.

There's no way to automatically reflect the additional dependencies from the requirements file, so the flake8 plugin list needs to be a verbatim copy.

resolves #7991

.pre-commit-config.yaml

@@ -9,11 +9,19 @@ repos:
     hooks:
       - id: isort
         name: isort (python)
+  - repo: https://github.com/pycqa/flake8
+    rev: 4.0.1  # must match requirements-tests.txt
+    hooks:
+      - id: flake8
+        additional_dependencies:
+          # must match requirements-tests.txt
+          - 'flake8-bugbear==21.11.29'
+          - 'flake8-pyi==22.5.1'
 
 ci:
     autofix_commit_msg: '[pre-commit.ci] auto fixes from pre-commit.com hooks'
     autofix_prs: true
     autoupdate_commit_msg: '[pre-commit.ci] pre-commit autoupdate'
     autoupdate_schedule: weekly
-    skip: []
+    skip: [flake8]
     submodules: false

requirements-tests.txt

@@ -2,6 +2,7 @@ mypy==0.960
 pytype==2022.6.6; platform_system != "Windows"
 # must match .pre-commit-config.yaml
 black==22.3.0
+# must match .pre-commit-config.yaml
 flake8==4.0.1
 flake8-bugbear==21.11.29
 flake8-pyi==22.5.1