Fix USE_TZ RemovedInDjango50Warning

Fix this warning, which appears in both the docs build and Django 4.0 tests:

```
/.../python3.8/site-packages/django/conf/__init__.py:199: RemovedInDjango50Warning: The default value of USE_TZ will change from False to True in Django 5.0. Set USE_TZ to False in your project settings if you want to keep the current default behavior.
```

Author: adamchainz

example/settings.py

@@ -57,6 +57,8 @@
     }
 ]
 
+USE_TZ = True
+
 WSGI_APPLICATION = "example.wsgi.application"
 
 

tests/panels/test_sql.py

@@ -121,7 +121,13 @@ def test_param_conversion(self):
             .filter(group_count__lt=10)
             .filter(group_count__gt=1)
         )
-        list(User.objects.filter(date_joined=datetime.datetime(2017, 12, 22, 16, 7, 1)))
+        list(
+            User.objects.filter(
+                date_joined=datetime.datetime(
+                    2017, 12, 22, 16, 7, 1, tzinfo=datetime.timezone.utc
+                )
+            )
+        )
 
         response = self.panel.process_request(self.request)
         self.panel.generate_stats(self.request, response)

tests/settings.py

@@ -69,6 +69,8 @@
     },
 ]
 
+USE_TZ = True
+
 STATIC_ROOT = os.path.join(BASE_DIR, "tests", "static")
 
 STATIC_URL = "/static/"

tests/test_forms.py

@@ -1,14 +1,14 @@
-from datetime import datetime
+from datetime import datetime, timezone
 
 from django import forms
 from django.test import TestCase
 
 from debug_toolbar.forms import SignedDataForm
 
-SIGNATURE = "v02QBcJplEET6QXHNWejnRcmSENWlw6_RjxLTR7QG9g"
+SIGNATURE = "-WiogJKyy4E8Om00CrFSy0T6XHObwBa6Zb46u-vmeYE"
 
-DATA = {"value": "foo", "date": datetime(2020, 1, 1)}
-SIGNED_DATA = f'{{"date": "2020-01-01 00:00:00", "value": "foo"}}:{SIGNATURE}'
+DATA = {"value": "foo", "date": datetime(2020, 1, 1, tzinfo=timezone.utc)}
+SIGNED_DATA = f'{{"date": "2020-01-01 00:00:00+00:00", "value": "foo"}}:{SIGNATURE}'
 
 
 class FooForm(forms.Form):
@@ -32,7 +32,7 @@ def test_verified_data(self):
             form.verified_data(),
             {
                 "value": "foo",
-                "date": "2020-01-01 00:00:00",
+                "date": "2020-01-01 00:00:00+00:00",
             },
         )
         # Take it back to the foo form to validate the datetime is serialized