Cannot execute Python3 on Win8.1

Hi, the issue has already been reported here, but maybe I can help by being more accurate.
I´m using Win8.1, Python 3.4.1 and Atom 1.0.16 with only two packages "atom.beatify" and "script (2.26.4)".
python is in the path and I start atom from the cmd, but nevertheless "script" isn´t able to execute a simple script as it doesn´t find python in the path. Please check attached pictures.

Is there any debug-log that might help ? For my understanding everything should be fine when I can start python from the path and start atom using the cmd-env.