Merge 3.3

Doc/library/contextlib.rst

@@ -279,11 +279,12 @@ Functions and classes provided:
 
          with ExitStack() as stack:
              files = [stack.enter_context(open(fname)) for fname in filenames]
-             close_files = stack.pop_all().close()
+             # Hold onto the close method, but don't call it yet.
+             close_files = stack.pop_all().close
              # If opening any file fails, all previously opened files will be
              # closed automatically. If all files are opened successfully,
              # they will remain open even after the with statement ends.
-             # close_files() can then be invoked explicitly to close them all
+             # close_files() can then be invoked explicitly to close them all.
 
    .. method:: close()