win_getpass(): if sys.stdin is not sys.__stdin__, use

default_getpass().  This should prevent hanging when it is called in
IDLE.

Fixes SF bug #455648.

Lib/getpass.py

@@ -42,6 +42,8 @@ def unix_getpass(prompt='Password: '):
 
 def win_getpass(prompt='Password: '):
     """Prompt for password with echo off, using Windows getch()."""
+    if sys.stdin is not sys.__stdin__:
+        return default_getpass(prompt)
     import msvcrt
     for c in prompt:
         msvcrt.putch(c)