This is only used for sound at present (see #1041) and it is blocked by the lack of released version of cx_freeze for python 3.5: https://bitbucket.org/anthony_tuininga/cx_freeze/pull-requests/83. But since trunk supports 3.5, we could always use a known working version (and snapshot it if necessary). Low priority.
The latest 3.4.5 release is no longer available as binaries for win32. Python 3.5 does not support XP... blocked by #678
Milestone renamed
The new MSYS2 build system (#678) does use python 3.5, but the broken cx_freeze code prevents us from using python3 for the sound subprocess (#1386).
Will re-visit if and when cx_freeze support improves.
Closing here, will follow up in #1386.
(edit milestone)
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1072