When an HTTP GET request fails, it's useful to go beyond the "not
successful" message, and show the code returned by the server.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Message-Id: <20210222193240.921250-3-crosa@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>