pull: for pull --update with failed update, print hint if any

An upcoming patch will add a hint to the abort message, and we don't want to
lose that here.

mercurial/commands.py

@@ -4527,6 +4527,8 b' def postincoming(ui, repo, modheads, opt'
             ret = hg.update(repo, checkout)
         except util.Abort, inst:
             ui.warn(_("not updating: %s\n") % str(inst))
+            if inst.hint:
+                ui.warn(_("(%s)\n") % inst.hint)
             return 0
         if not ret and not checkout:
             if bookmarks.update(repo, [movemarkfrom], repo['.'].node()):