Updated to latest release 3.3.17. Remove py26 incompatibility directive.
This seems to have been fixed in a previous version. At least "import
billiard" works from the interpreter. From CHANGES.txt:

- Fixes SemLock on Python 3.4 (Issue #107) when using
  ``forking_enable(False)``.

- Pool: Include more useful exitcode information when processes exit.

(rodent)