def METHOD_NAME(self):
    create_user('testuser', email='testuser@example.com')
    response = self.client.post(self.url, {
        'username': 'test',
        'password1': 'test',
        'password2': 'test',
        'email': 'testuser@example.com'
    })
    self.assertEqual(response.status_code, 200)
    selector = htmls.S(response.content)
    self.assertEqual(
        selector.one('#id_email_wrapper .message--error').alltext_normalized,
        'Account with this email address already exists.')