update docstring

Author: tfeldmann

fs/move.py

@@ -137,6 +137,11 @@ def move_dir(
         preserve_time (bool): If `True`, try to preserve mtime of the
             resources (defaults to `False`).
 
+    Raises:
+        fs.errors.ResourceNotFound: if ``src_path`` does not exist on `src_fs`
+        fs.errors.DirectoryExpected: if ``src_path`` or one of its
+            ancestors is not a directory.
+        fs.errors.IllegalDestination: when moving a folder into itself
     """
     with manage_fs(src_fs, writeable=True) as _src_fs:
         with manage_fs(dst_fs, writeable=True, create=True) as _dst_fs: