test_check_url_available: adjust message for requests 2.27.0
Improved error text for misnamed InvalidSchema and MissingSchema exceptions. https://github.com/psf/requests/blob/v2.27.0/HISTORY.md#2270-2022-01-03
Improved error text for misnamed InvalidSchema and MissingSchema exceptions. https://github.com/psf/requests/blob/v2.27.0/HISTORY.md#2270-2022-01-03