Thomas Hervé merged his process/pty-process branch into Twisted trunk today. He's been working on integrating the two separate implementations of POSIX child process creation in Twisted, one for child processes connected to a PTY and one for child processes connected to a set of pipes. A long time ago, someone copied an entire class full of code and started twiddling it to support PTYs. This led to a lot of duplication, obviously, and some bugs where the two classes diverged.
With this re-unification, some behavior which was inconsistent between the two variations has been removed, some bugs which were present in one or the other of the two classes have been fixed, and a lot of duplicate code has been completely eliminated. Best of all, there is now some actual unit test coverage for this code (it was originally developed long before Twisted's current high testing requirements) and a test double which will make it easier to write more and better unit tests for this code in the future.
One other piece of fall out is that on Windows, if application code tries to signal an already-exited process, an exception will be raised indicating that it is not possible to do so. This brings Windows process support closer still to POSIX process support.