This is reproducible on both 2.7.13 and 3.6.1.

Please refer to the attached files for demonstration. It seems that when I spawn a python script using getpass.getpass() from expect (http://expect.sourceforge.net/ - I'm using version 5.45), the input is not passed. Further, it seems interactive control is handed over to the shell- however, it doesn't actually pass anything to the python script that was spawned, forcing one to break out of the expect process itself.

Obviously, the proofs attached require the expect binary to be installed. To test, simply mark "poc.exp" as executable and execute it (assuming poc.py is in the same directory. If not, you'll need to edit line 4 of poc.exp).