I set a daily fetch for my custom rss,and don't know how to get a cover for them.
define default_cover(cover_file) = '/xxx/xxx.png'
define default_cover(cover_file) = 'http://xw.xx/xx.png'
define default_cover(cover_file) = /xxx/xxx.png
define default_cover(cover_file) =
http://xw.xx/xx.png
try them all and didn't work