Use the preferred form of raise statements in the docs.
diff --git a/Doc/library/signal.rst b/Doc/library/signal.rst
index 3793a89..c039eee 100644
--- a/Doc/library/signal.rst
+++ b/Doc/library/signal.rst
@@ -232,7 +232,7 @@
 
    def handler(signum, frame):
        print 'Signal handler called with signal', signum
-       raise IOError, "Couldn't open device!"
+       raise IOError("Couldn't open device!")
 
    # Set the signal handler and a 5-second alarm
    signal.signal(signal.SIGALRM, handler)