histedit: notice when the main window underflows height and abort If you try to have a 13-line-tall terminal and use curses histedit, it fails by spinning in an infinite loop due to the catch-all ignore of curses errors on line 1682 of histedit.py. We should also fix that catch-all ignore of curses errors (what other demons lurk here, I wonder?) but we can trivially catch this case and guide the user to a happy path. We've seen this mostly in IDE users that have a tendency to have really tiny embedded terminal windows. Differential Revision: https://phab.mercurial-scm.org/D9854