Merge pull request #2148 from bfroehle/no_more_os_system win32 iptest: Use subprocess.Popen() instead of os.system(). The call to `os.system` in `iptest` prevents us from easily setting `$IPYTHONDIR` to a temporary directory. In theory we should be able to use `subprocess.Popen` instead of `os.system` in Windows. This would unify the code structure and make it easy to pass in a different environment. Note that Python < 2.7 does not have `os.kill`. I've attempted to work around this by using `ctypes` to kill any living processes.