Switch to pre-release of Django 4.1

Author: thibaudcolas

tox.ini

@@ -14,7 +14,9 @@ deps =
     dj22: Django>=2.2,<2.3
     dj32: Django>=3.2,<3.3
     dj40: Django>=4.0,<4.1
-    dj41: Django>=4.1,<4.2
+    ; Switch to version range upon stable release.
+    ; dj41: Django>=4.1,<4.2
+    dj41: Django==4.1a1
     djmain: https://github.com/django/django/archive/main.zip
 
 [testenv:lint]