Fix #1731: Test against Django 4.2a1 (main is already in there)

Author: matthiask

docs/changes.rst

@@ -4,6 +4,7 @@ Change log
 Pending
 -------
 
+* Added Django 4.2a1 to the CI.
 * Fixed PostgreSQL raw query with a tuple parameter during on explain.
 * Use ``TOOLBAR_LANGUAGE`` setting when rendering individual panels
   that are loaded via AJAX.

tox.ini

@@ -4,14 +4,15 @@ envlist =
     docs
     packaging
     py{37}-dj{32}-{sqlite,postgresql,postgis,mysql}
-    py{38,39,310}-dj{32,40,41,main}-{sqlite,postgresql,postgis,mysql}
-    py{311}-dj{41,main}-{sqlite,postgresql,postgis,mysql}
+    py{38,39}-dj{32,40,41,42}-{sqlite,postgresql,postgis,mysql}
+    py{310,311}-dj{41,42,main}-{sqlite,postgresql,postgis,mysql}
 
 [testenv]
 deps =
     dj32: django~=3.2.9
     dj40: django~=4.0.0
     dj41: django~=4.1.3
+    dj42: django>=4.2a1,<5
     postgresql: psycopg2-binary
     postgis: psycopg2-binary
     mysql: mysqlclient