Thank you.
But it doesn't seem to work. It is somthing like this:
SET HTTPS_PROXY=127.0.0.1:56888 butler push -v C:\...\desktoptree_itchio\background.png utstudio/desktoptree:test
Still the same result. The proxy setting seem to be in effect(and I have already tested it in IE and chrome), because if I change it to a false value, it says "Version check failed".