Use service as hostname fallback to enable keyring usage on redirects

[miguelnmiranda]

Description

When following redirects that don't point to one of the configured indexes pip will request credentials from the keyrings using the netloc taken from the target's location url (ref).

The present implementation relies on urlib.urlparse to determine hostname (which is part of netloc). urlparse requires urls to have a schema (or at least //) in order to detect a netloc (ref), which makes it misclassify a previously parsed netloc as a path (ref).

I proposed falling back to using the service as is when a hostname cannot be found (ex. when service is just a url's netloc).

Motivation

Using a private pypi server that redirects to a GCP Artifact Registry Python repository for certain dependencies.

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[miguelnmiranda]

@megan-kuo Hi Megan, could you have a look at this PR please?

[megan-kuo]

Thanks @miguelnmiranda! so sorry its taken me this long to respond, I'm OOO this week but will most definitely get to it next week - just wanted to drop by to say this item is on my to do list.

Thanks again!

[miguelnmiranda]

@megan-kuo Hi Megan, Please provide guidance on how to move this forward.