Handle windows paths better and utilize this utility for creating the virtualenv path.

[matteius]

The issue

Windows was having issues creating new virtualenvs after this patch: #5686

There were two types of issues:

• sometimes the windows PATH may come from an env var in gitbash shell as \ instead of /
• It was sometimes double appending the drive and creating a new directory structure for the virtualenv home.

The fix

Fix PATH edge case in pythonfinder==2.0.2

Declining on a news fragment since the issue was never published in a pipenv release.

The checklist

• Associated issue
• A news fragment in the news/ directory to describe this fix with the extension .bugfix.rst, .feature.rst, .behavior.rst, .doc.rst. .vendor.rst. or .trivial.rst (this will appear in the release changelog). Use semantic line breaks and name the file after the issue number or the PR #.