multiple times subprocess fails on windows

[kvbik]

Hello,

in a test suite in my project (called rvirtualenv [1]) I discovered a
strange behaviour when calling from python a batch file which calles
another python and this calles a shell command.

[1] http://github.com/kvbik/rvirtualenv

I know it sounds pretty strange, but I do this only because I am
testing such specific tool (that has similar functionality like
original virtualenv and there are things like activate.bat commands).

I've uploaded some code snippet here:

https://gist.github.com/709004/6ccc44d6aed5fe694bb2adbef2400bbea92998a1

If anyone could explain me this behaviour I would be more than happy,
because right now it is the only failing test in my project ;).

Thanks in advance, Jakub..