more accure error reporting for OSFS.open

fs/osfs/__init__.py

@@ -157,6 +157,7 @@ class OSFS(OSFSXAttrMixin, OSFSWatchMixin, FS):
         except EnvironmentError, e:
             #  Win32 gives EACCES when opening a directory.
             if sys.platform == "win32" and e.errno in (errno.EACCES,):
+                if self.isdir(path):
                     raise ResourceInvalidError(path)
             raise