[Checkins] [zopefoundation/zope.proxy] bfd0d6: Use MacPython 3.6.2.

[Jason Madden]

  Branch: refs/heads/isue-3.6.2
  Home:   https://github.com/zopefoundation/zope.proxy
  Commit: bfd0d6146ec88386ee5083302e5eb8c0d2d925e3
      https://github.com/zopefoundation/zope.proxy/commit/bfd0d6146ec88386ee5083302e5eb8c0d2d925e3
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2020-01-20 (Mon, 20 Jan 2020)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Use MacPython 3.6.2.

Fixes issue uploading coverage.

Also add mac 3.8