[Checkins] [zopefoundation/zope.interface] cc4af2: Install twine into a new virtualenv, not globally

[Marius Gedminas]

  Branch: refs/heads/fix-macos-maybe
  Home:   https://github.com/zopefoundation/zope.interface
  Commit: cc4af28d0af269e1d1066181c1a99c17ecfb3a97
      https://github.com/zopefoundation/zope.interface/commit/cc4af28d0af269e1d1066181c1a99c17ecfb3a97
  Author: Marius Gedminas <marius at gedmin.as>
  Date:   2019-11-11 (Mon, 11 Nov 2019)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Install twine into a new virtualenv, not globally