Test Installation not working on Windows

[superbonaci]

Latest firefox and extension, python command run from command line:

python.exe open_with_windows.py
Open With native helper, version 7.2.3.

ExtensionError: No such native application open_with ExtensionUtils.jsm:56:5
    ExtensionError resource://gre/modules/ExtensionUtils.jsm:56
    startupPromise resource://gre/modules/NativeMessaging.jsm:83
this.ports.get(...) is undefined ExtensionParent.jsm:351
    recvPortMessage resource://gre/modules/ExtensionParent.jsm:351
    recvPortMessage self-hosted:844
    _recv resource://gre/modules/ConduitsChild.jsm:78
    receiveMessage resource://gre/modules/ConduitsParent.jsm:333