Add note to Queue.get() docs about block=True (GH-2223)

Doc/library/queue.rst

@@ -150,6 +150,11 @@ provide the public methods described below.
    Otherwise (*block* is false), return an item if one is immediately available,
    else raise the :exc:`Empty` exception (*timeout* is ignored in that case).
 
+   Prior to 3.0 on POSIX systems, and for all versions on Windows, if
+   *block* is true and *timeout* is ``None``, this operation goes into
+   an uninterruptible wait on an underlying lock. This means that no exceptions
+   can occur, and in particular a SIGINT will not trigger a :exc:`KeyboardInterrupt`.
+
 
 .. method:: Queue.get_nowait()