Fixed #25163 -- Added hint for non-staff users to admin login page.

django/contrib/admin/templates/admin/login.html

@@ -31,6 +31,16 @@
 {% endif %}
 
 <div id="content-main">
+
+{% if user.is_authenticated %}
+<p class="errornote">
+{% blocktrans with username=request.user.username %}
+    You are authenticated as {{ username }}, but are not authorized to
+    access this page. Would you like to login to a different account?
+{% endblocktrans %}
+</p>
+{% endif %}
+
 <form action="{{ app_path }}" method="post" id="login-form">{% csrf_token %}
   <div class="form-row">
     {{ form.username.errors }}

tests/admin_views/tests.py

@@ -1558,6 +1558,25 @@ class AdminViewPermissionsTest(TestCase):
         self.assertFalse(login.context)
         self.client.get(reverse('admin:logout'))
 
+    def test_login_page_notice_for_non_staff_users(self):
+        """
+        A logged-in non-staff user trying to access the admin index should be
+        presented with the login page and a hint indicating that the current
+        user doesn't have access to it.
+        """
+        hint_template = 'You are authenticated as {}'
+
+        # Anonymous user should not be shown the hint
+        response = self.client.get(self.index_url, follow=True)
+        self.assertContains(response, 'login-form')
+        self.assertNotContains(response, hint_template.format(''), status_code=200)
+
+        # Non-staff user should be shown the hint
+        self.client.login(**self.nostaff_login)
+        response = self.client.get(self.index_url, follow=True)
+        self.assertContains(response, 'login-form')
+        self.assertContains(response, hint_template.format(self.u6.username), status_code=200)
+
     def test_add_view(self):
         """Test add view restricts access and actually adds items."""