Issue #16714: use 'raise' exceptions, don't 'throw'.

Patch by Serhiy Storchaka.

Lib/contextlib.py

@@ -151,7 +151,7 @@ class ExitStack(object):
             files = [stack.enter_context(open(fname)) for fname in filenames]
             # All opened files will automatically be closed at the end of
             # the with statement, even if attempts to open files later
-            # in the list throw an exception
+            # in the list raise an exception
 
     """
     def __init__(self):