This is a Task to discuss this upstream patch:
The summary was:
Mercurial 6.4 was recently released and showing up in package managers. With
the update to 6.4 using arc land would result in an exception indicating that
expandpath function does not exist.
The ui.expandpath function was deprecated in 5.8 and now removed in 6.4. The
functionality has been moved to utils.urlutil.get_ functions (they are split
between getting pull, push, and clone paths).
This updates the script to try utils.urlutil.get_clone_path function if the
ui.expandpath function is not present.