Add django==4.0a1 to the build matrix

.github/workflows/ci.yml

@@ -32,12 +32,18 @@ jobs:
     strategy:
       matrix:
         python-version: [3.5, 3.6, 3.7, 3.8, 3.9]
-        django-version: [2.2, 3.1, 3.2]
+        django-version: [2.2, 3.1, 3.2, 4.0a1]
         exclude:
             - python-version: 3.5
               django-version: 3.1
             - python-version: 3.5
               django-version: 3.2
+            - python-version: 3.5
+              django-version: 4.0a1
+            - python-version: 3.6
+              django-version: 4.0a1
+            - python-version: 3.7
+              django-version: 4.0a1
             - python-version: 3.8
               django-version: 2.2
             - python-version: 3.9

.pre-commit-config.yaml

@@ -1,6 +1,6 @@
 repos:
 -   repo: https://github.com/ambv/black
-    rev: stable
+    rev: 21.9b0
     hooks:
     - id: black
       language_version: python3.7

tox.ini

@@ -4,11 +4,11 @@ envlist =
     py35-{2.2},
     py36-{2.2,3.1,3.2,master},
     py37-{2.2,3.1,3.2,master},
-    py38-{3.1,3.2,master},
+    py38-{3.1,3.2,4.0,master},
+    py39-{3.2,4.0,master}
     docs,
     flake8,
     isort,
-    black
 
 [testenv]
 basepython =
@@ -28,6 +28,7 @@ deps =
     2.2: Django==2.2.*
     3.1: Django==3.1.*
     3.2: Django==3.2.*
+    4.0: Django==4.0a1
     master: https://github.com/django/django/archive/master.tar.gz
     coverage
     -r{toxinidir}/requirements/common.pip
@@ -50,16 +51,10 @@ deps = flake8==3.7.9
 commands = flake8
 
 [flake8]
-ignore = E731,W503,E203
+ignore = E731,W503,E203j
 exclude = .git,__pycache__,.tox,example/app/migrations
 max-line-length = 120
 
-[testenv:black]
-basepython = python3.8
-passenv = LC_CTYPE
-deps = black==19.10b0
-commands = black --check .
-
 [testenv:isort]
 basepython = python3.8
 deps =