Log Message:
py-setuptools: update to 38.5.1.

v38.5.1
-------

* #1271: Revert to Cython legacy ``build_ext`` behavior for
  compatibility.

v38.5.0
-------

* #1229: Expand imports in ``build_ext`` to refine detection of
  Cython availability.

* #1270: When Cython is available, ``build_ext`` now uses the
  new_build_ext.