Issue #3178273 by longwave: BasicAuthTestTrait::basicAuthPostForm() does not work

    return $this->drupalGet($path, $options, $this->getBasicAuthHeaders($username, $password));

  }

  /**

   * Executes a form submission using basic authentication.

   *

   * @param string $path

   *   Location of the post form.

   * @param array $edit

   *   Field data in an associative array.

   * @param string $submit

   *   Value of the submit button whose click is to be emulated.

   * @param string $username

   *   The username to use for basic authentication.

   * @param string $password

   *   The password to use for basic authentication.

   * @param array $options

   *   Options to be forwarded to the url generator.

   * @param string $form_html_id

   *   (optional) HTML ID of the form to be submitted.

   * @param string $extra_post

   *   (optional) A string of additional data to append to the POST submission.

   *

   * @return string

   *   The retrieved HTML string.

   *

   * @see \Drupal\simpletest\WebTestBase::drupalPostForm()

   */

  protected function basicAuthPostForm($path, $edit, $submit, $username, $password, array $options = [], $form_html_id = NULL, $extra_post = NULL) {

    return $this->drupalPostForm($path, $edit, $submit, $options, $this->getBasicAuthHeaders($username, $password), $form_html_id, $extra_post);

  }

  /**

   * Returns HTTP headers that can be used for basic authentication in Curl.

   *