credentials for http proxy when using default_urllb3_manager()

[jelmer]

I need to clone a git+https:// repo behind an HTTP proxy. Unfortunately, Poetry will rely on the default urllib3.PoolManager generated by default_urllib3_manager() (code). And that default generator misses a critical part: it won't populate the credentials in the proxy_header parameter.

This is a critical part because HTTPS over HTTP proxy requires tunneling (see urllib3 implementation connection_requires_http_tunnel() here)

... and when using tunneling, the proxy credentials should be in Proxy-Authorization: Basic XXXX header. Otherwise it is nowhere else.

Suggestion: when proxy_url contains a username+password => populate the proxy_header with Proxy-Authorization: Basic XXXX

Originally posted by @raphaeljoie in #822 (comment)

[jelmer]

We're passing proxy_url (including any credentials) to ProxyManager. If the authentication header needs to be constructed manually, happy to merge a PR that splits the URL and passes proxy_headers.

[mallport]

We have the same issue here. Would be great if this was addressed.