Fix pyenv as it is broken on new pythonfinder version.

[matteius]

Vendor in pythonfinder==2.0.1

Backstory:

I discovered that pyenv was broken with the new pythonfinder. It was trying to install the system python and alerting that it was different than what was called out in the Pipfile. Despite pyenv being installed, it did nothing to try and use those versions.

This also cleans up some other edge cases around pyenv:

• Ensures the shims directories will not be included (there was logic for this in there, but the paths weren't matching)
• Ensures the version directories are included on the PATH