chore: test against Django 5.2dev

tox.ini

@@ -3,14 +3,15 @@
 envlist =
         py{39,310,311}-django42,
         py{310,311,312}-django{50,51},
+        py312-django52,
         py{39,310}-django42-jinja2,
         py{310,311}-django{42,50}-jinja2,
         py312-django{50,51}-jinja2,
         gettext,flake8,docs,coverage
 
 [gh-actions]
 python =
-  3.12: py312-django50, py312-django51, py312-django51-jinja2
+  3.12: py312-django50, py312-django51, py312-django52, py312-django51-jinja2
   3.11: p311-django-51, p311-django-50, p311-django-50-jinjia, p311-django-42, p311-django-42-jinjia
   3.10: py310-django42, py310-django42-jinja2, py310-django50, py310-django51, py310-django50-jinja2
   3.9: py39-django42, py39-django42-jinja2
@@ -27,6 +28,7 @@ deps =
         django42: Django>=4.2a,<4.3
         django50: Django>=5.0a,<5.1
         django51: Django>=5.1,<5.2
+        django52: https://github.com/django/django/tarball/main
         py{39,310,311,312}-django{42,50}: python3-memcached
         jinja2
         Pillow
@@ -53,7 +55,7 @@ commands = python -Wd manage.py test captcha --settings jinja2_settings
 
 
 [testenv:gettext]
-basepython = python3.9
+basepython = python3.12
 changedir = captcha/locale/
 allowlist_externals =
       msgfmt
@@ -80,13 +82,13 @@ commands =
       msgfmt -c -o zh_Hans/LC_MESSAGES/django.mo zh_Hans/LC_MESSAGES/django.po
 
 [testenv:flake8]
-basepython = python3.9
-deps = flake8==3.9.2
+basepython = python3.12
+deps = flake8
 commands=
     flake8 {toxinidir}/captcha
 
 [testenv:docs]
-basepython = python3.9
+basepython = python3.12
 deps =
         sphinx
         sphinx-book-theme