[Checkins] [zopefoundation/DocumentTemplate] e91bd4: Work around travis-ci / setuptools problem.

[GitHub]

  Branch: refs/heads/travis
  Home:   https://github.com/zopefoundation/DocumentTemplate
  Commit: e91bd41fc9e56f123c315e93132fae0c1576caa4
      https://github.com/zopefoundation/DocumentTemplate/commit/e91bd41fc9e56f123c315e93132fae0c1576caa4
  Author: Hanno Schlichting <hanno at hannosch.eu>
  Date:   2017-09-09 (Sat, 09 Sep 2017)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Work around travis-ci / setuptools problem.

The travis-ci Python 3.6 image contains the faulty setuptools 36.2.0
which again has a problem downgrading itself, but only if other things
are installed at the same time.