Add test for Public role permissions. (#13965)

In #13923, all permissions were removed from the Public role. This adds a test to ensure that the default public role doesn't have any permissions.

related: #13923
(cherry picked from commit a52e77d0b4)

tests/www/test_security.py

@@ -169,6 +169,12 @@ class TestSecurity(unittest.TestCase):
 
         assert role_perms_len == new_role_perms_len
 
+    def test_verify_public_role_has_no_permissions(self):
+        with self.app.app_context():
+            public = self.appbuilder.sm.find_role("Public")
+
+            assert public.permissions == []
+
     def test_get_user_roles(self):
         user = mock.MagicMock()
         user.is_anonymous = False