[Checkins] [zopefoundation/persistent] 39017d: Use Python 3.6.1 on MacOS

[Marius Gedminas]

  Branch: refs/heads/macpython-3.6
  Home:   https://github.com/zopefoundation/persistent
  Commit: 39017d911c1703f076b3778703101ad733580a6d
      https://github.com/zopefoundation/persistent/commit/39017d911c1703f076b3778703101ad733580a6d
  Author: Marius Gedminas <marius at gedmin.as>
  Date:   2020-01-17 (Fri, 17 Jan 2020)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Use Python 3.6.1 on MacOS

It seems that 3.6.0 has a bug that causes
https://github.com/nedbat/coveragepy/issues/703 ("Couldn't use data file
'/Users/travis/build/zopefoundation/persistent/.coverage': Safety level
may not be changed inside a transaction" and a failed build from
'coverage run').