grader works with url

Signed-off-by: Yury Tsarev <ytsarev@suse.com>
DRY the code

Signed-off-by: Yury Tsarev <ytsarev@suse.com>
Extend checks. Move availability check to proper callback function.

Signed-off-by: Yury Tsarev <ytsarev@suse.com>