Update pipenv version

[harrywhite4]

An issue with pipenv's --system --deploy options has been fixed in a newer release as described here
https://github.com/pypa/pipenv/blob/master/HISTORY.txt#L95

This was likely the casue of #704 and #702 so it would be nice to switch to the latest version

[sigmavirus24]

Yes, and looking through the issues opened since 2018.6.25 and 2018.7.1 there are significant issues with packages using {git = ...} and some other issues. Unfortunately no matter what version of pipenv we pick, it will be problematic for a good portion of users.

See also:

• Package from Pipfile.lock ignored because of last (irrelevant) marker not matching pypa/pipenv#2520
• Can't lock package with git and extras pypa/pipenv#2504
• index_indicators check needs improvement. pypa/pipenv#2494

[harrywhite4]

I understand it's difficult to find a version that everyone will be happy with. Being able to set an environment variable to override the version might be a better solution

[sigmavirus24]

Perhaps an OVERRIDDEN_PIPENV_VERSION that overrides our default?

[techalchemy]

@sigmavirus24 if you file issues with us or you let me know directly about things that impact your pipeline I can triage these more effectively -- my company has an enterprise account with heroku and these do have an impact on me too so I'm happy to help

[sigmavirus24]

@techalchemy I referenced exactly the issues that would be blockers above. It sounds like you're expecting something else though, what do you think I should have done differently?

[harrywhite4]

Closing in favor of #732