issue27186: add open/io.open; patch by Jelle Zijlstra
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index c3563f3..6f7ba1f 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -878,11 +878,11 @@
    Open *file* and return a corresponding :term:`file object`.  If the file
    cannot be opened, an :exc:`OSError` is raised.
 
-   *file* is either a string or bytes object giving the pathname (absolute or
-   relative to the current working directory) of the file to be opened or
-   an integer file descriptor of the file to be wrapped.  (If a file descriptor
-   is given, it is closed when the returned I/O object is closed, unless
-   *closefd* is set to ``False``.)
+   *file* is either a string, bytes, or :class:`os.PathLike` object giving the
+   pathname (absolute or relative to the current working directory) of the file
+   to be opened or an integer file descriptor of the file to be wrapped.  (If a
+   file descriptor is given, it is closed when the returned I/O object is
+   closed, unless *closefd* is set to ``False``.)
 
    *mode* is an optional string that specifies the mode in which the file is
    opened.  It defaults to ``'r'`` which means open for reading in text mode.