[3.8] bpo-41661: Document os.path.relpath() exception on Windows with different drives (GH-25346)#25367

ambv merged 1 commit intopython:3.8python/cpython:3.8from

miss-islington:backport-67c0b3d-3.8miss-islington/cpython:backport-67c0b3d-3.8Copy head branch name to clipboard