[Checkins] [zopefoundation/DateTime] 733f15: Fix PyPy on TravisCI. (#16)

[Michael Howitz]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/DateTime
  Commit: 733f157e653758478bc935684950b08d7dc46e7b
      https://github.com/zopefoundation/DateTime/commit/733f157e653758478bc935684950b08d7dc46e7b
  Author: Michael Howitz <mac at gmx.net>
  Date:   2019-06-29 (Sat, 29 Jun 2019)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Fix PyPy on TravisCI. (#16)

Upgrade to xenial  fixes PyPy on Travis.