[Checkins] [zopefoundation/BTrees] 5aae58: Cleanups from review.

[GitHub]

  Branch: refs/heads/issue78
  Home:   https://github.com/zopefoundation/BTrees
  Commit: 5aae589d08ae92914235bc2cd7ad9fae4f97e260
      https://github.com/zopefoundation/BTrees/commit/5aae589d08ae92914235bc2cd7ad9fae4f97e260
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2018-03-08 (Thu, 08 Mar 2018)

  Changed paths:
    M BTrees/_compat.py
    M BTrees/tests/common.py
    M BTrees/tests/testBTreesUnicode.py
    M setup.py
    M tox.ini

  Log Message:
  -----------
  Cleanups from review.

Detect pip installs with 'bdist_wheel' (or manual builds for upload) and don't let the C extensions fail to build unless PURE_PYTHON is set.