Fixed #33132 -- Fixed test client handling of querystring only redirects.

Regression in 1e5aa8e1c7.

tests/test_client/tests.py

@@ -291,6 +291,13 @@ class ClientTest(TestCase):
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response.request['PATH_INFO'], '/accounts/login/')
 
+    def test_redirect_to_querystring_only(self):
+        """A URL that consists of a querystring only can be followed"""
+        response = self.client.post('/post_then_get_view/', follow=True)
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.request['PATH_INFO'], '/post_then_get_view/')
+        self.assertEqual(response.content, b'The value of success is true.')
+
     def test_follow_307_and_308_redirect(self):
         """
         A 307 or 308 redirect preserves the request method after the redirect.

tests/test_client/urls.py

@@ -8,6 +8,7 @@ urlpatterns = [
     path('upload_view/', views.upload_view, name='upload_view'),
     path('get_view/', views.get_view, name='get_view'),
     path('post_view/', views.post_view),
+    path('post_then_get_view/', views.post_then_get_view),
     path('put_view/', views.put_view),
     path('trace_view/', views.trace_view),
     path('header_view/', views.view_with_header),

tests/test_client/views.py

@@ -85,6 +85,21 @@ def post_view(request):
     return HttpResponse(t.render(c))
 
 
+def post_then_get_view(request):
+    """
+    A view that expects a POST request, returns a redirect response
+    to itself providing only a ?success=true querystring,
+    the value of this querystring is then rendered upon GET.
+    """
+    if request.method == 'POST':
+        return HttpResponseRedirect('?success=true')
+
+    t = Template('The value of success is {{ value }}.', name='GET Template')
+    c = Context({'value': request.GET.get('success', 'false')})
+
+    return HttpResponse(t.render(c))
+
+
 def json_view(request):
     """
     A view that expects a request with the header 'application/json' and JSON