Log Message:
py-billiard: updated to 3.6.0.0

3.6.0.0:
- Add support of sending parent process death signal.
- Previous fix for handling timeouts caused a problem in warm shutdowns due
  to use of deepcopy.
  We now use a shallow copy of the cache and do so only when it is needed.
- Cleanup old checks and workarounds for Python versions we no longer support.