Fix python script calling on Windows.

On Windows a python file without extension is not runnable by itself, it needs the python executable.

Change-Id: I99cbfadc790acf3b3205faf6b940c26fb3c71e89
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>
Reviewed-by: Andras Becsi <andras.becsi@digia.com>