[Checkins] [zopefoundation/BTrees] cc4a13: Build using newer manylinux image.

[Jason Madden]

  Branch: refs/heads/update-manylinux
  Home:   https://github.com/zopefoundation/BTrees
  Commit: cc4a13f35463efa5f2ab2cab749e7254a76837d6
      https://github.com/zopefoundation/BTrees/commit/cc4a13f35463efa5f2ab2cab749e7254a76837d6
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2019-11-08 (Fri, 08 Nov 2019)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  Build using newer manylinux image.

And update macOS python to 2.7.17 to try to fix uploads.