[Checkins] [zopefoundation/zope.session] bd4320: Fix test compatibility with ZODB 5.3.0

[GitHub]

  Branch: refs/heads/py36
  Home:   https://github.com/zopefoundation/zope.session
  Commit: bd4320548fcc0471b374540ecf43af3023590c27
      https://github.com/zopefoundation/zope.session/commit/bd4320548fcc0471b374540ecf43af3023590c27
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2017-09-22 (Fri, 22 Sep 2017)

  Changed paths:
    M .travis.yml
    M src/zope/session/api.rst

  Log Message:
  -----------
  Fix test compatibility with ZODB 5.3.0

Open files can now be pickled under Python 2.

We had to switch to a custom object: open sockets can be pickled under
PyPy, which was the only other trivial stdlib example I could think
of. This way, at least, we're guaranteed it never happens again.