A temporary workaround for pip 18.1 issues

[fridex]

A quick workaround to fix #2924, not tested. If acked, please release a new version of Pipenv not to keep systems failing on every new Pipenv installation.

[Froskekongen]

Since this has happened before, wouldn't a long-term solution be to always pin pip to versions that work, and for a new release check if newer versions of pip is acceptable?

What would be better options? I am asking because I really need to have control of a (very) large python environment.

[uranusjr]

@Froskekongen The long-term solution is to refactor pip and extract common parts into their own library, so we can have a stable Python API independent to pip releases. This is already being worked on, but pip’s code base is not very easy to work with.

For short-term (or middle-term), the best way to help would be to constantly help test Pipenv against the master branch of pip, and alert us if anything is failing.

[greysteil]

@techalchemy / @fridex I think this PR can be closed now we have 2018.10.9 🎉