fix typos, mostly in comments
diff --git a/Lib/test/test_threadsignals.py b/Lib/test/test_threadsignals.py
index fcae312..51e3d97 100644
--- a/Lib/test/test_threadsignals.py
+++ b/Lib/test/test_threadsignals.py
@@ -21,7 +21,7 @@
     return usr1, usr2, alrm
 
 
-# The signal handler. Just note that the signal occured and
+# The signal handler. Just note that the signal occurred and
 # from who.
 def handle_signals(sig,frame):
     signal_blackboard[sig]['tripped'] += 1