418 

   419 @contextlib.contextmanager

   420 def uninterruptable(warn):

   421     """Inhibit SIGINT handling on a region of code.

   422 

   423     Note that if this is called in a non-main thread, it turns into a no-op.

   424 

   425     Args:

   426       warn: A callable which takes no arguments, and returns True if the

   427             previous signal handling should be restored.

   428     """

   429 

   430     oldsiginthandler = [signal.getsignal(signal.SIGINT)]

   431     shouldbail = []

   432 

   433     def disabledsiginthandler(*args):

   434         if warn():

   435             signal.signal(signal.SIGINT, oldsiginthandler[0])

   436             del oldsiginthandler[0]

   437         shouldbail.append(True)

   438 

   439     try:

   440         try:

   441             signal.signal(signal.SIGINT, disabledsiginthandler)

   442         except ValueError:

   443             # wrong thread, oh well, we tried

   444             del oldsiginthandler[0]

   445         yield

   446     finally:

   447         if oldsiginthandler:

   448             signal.signal(signal.SIGINT, oldsiginthandler[0])

   449         if shouldbail:

   450             raise KeyboardInterrupt