Log Message:
py-test-xdist: updated to 1.22.5

pytest-xdist 1.22.5:
Bug Fixes
- Revert change that dropped support for pytest<3.4 and require six.
  This change caused problems in some installations, and was a mistaken
  in the first place as we should not change version requirements
  in bug-fix releases unless they fix an actual bug.

pytest-xdist 1.22.4:
Bug Fixes
- Remove last references to obsolete py.code.
  Remove some unnecessary references to py.builtin.
- Workaround cpu detection on Travis CI.