bpo-6689: os.path.commonpath raises ValueError for different drives isn't documented...

It would raise ValueError("Paths don't have the same drive") if the paths on different drivers, which is not documented.

os.path.commonpath raises ValueError when the *paths* are in different drivers, but it is not documented.
Update the document according @Windsooon 's suggestion.
It actually raise ValueError according line 355 of [test of path](https://github.com/python/cpython/blob/master/Lib/test/test_ntpath.py)

https://bugs.python.org/issue6689

diff --git a/Doc/library/os.path.rst b/Doc/library/os.path.rst
index 8e7ee8bfe7845fe6a5b6d3933a16f2052f31dff2..a673b81278ea7442fcd1bf91d182bbae6b9412de 100644 (file)
--- a/Doc/library/os.path.rst
+++ b/Doc/library/os.path.rst
@@ -87,9 +87,10 @@ the :mod:`glob` module.)
 .. function:: commonpath(paths)
 
    Return the longest common sub-path of each pathname in the sequence
-   *paths*.  Raise :exc:`ValueError` if *paths* contains both absolute and relative
-   pathnames, or if *paths* is empty.  Unlike :func:`commonprefix`, this
-   returns a valid path.
+   *paths*.  Raise :exc:`ValueError` if *paths* contain both absolute
+   and relative pathnames, the *paths* are on the different drives or
+   if *paths* is empty.  Unlike :func:`commonprefix`, this returns a
+   valid path.
 
    .. availability:: Unix, Windows.