https through an http-only proxy?
Solution 1:
Beware when you set http_proxy and https_proxy, normally you should set them at the same URL including the schema part, example:
http_proxy=http://your_proxy:proxy_port
https_proxy=http://your_proxy:proxy_port
Notice that both are in HTTP. That tells you the protocol your proxy uses, not the target website's schema, which can be HTTP or HTTPS, that is not related.
When, using the proxy for connecting to a HTTPS website, the proxy works in TCP mode, and (I'm simplifying here) your TCP connection passes through the proxy carrying encrypted packets from your client to the target website.
So, try setting your https_proxy environment variable the same as your http_proxy and hope you're allowed to use the CONNECT method.