$ cat /tmp/squashfs-args.diff 
--- ./snap.py.orig	2016-02-23 12:51:52.652917979 -0600
+++ snap.py	2016-02-23 12:54:58.968621187 -0600
@@ -76,6 +76,9 @@
     snap_name = _format_snap_name(snap)
 
     logger.info('Snapping {}'.format(snap_name))
+    # These options need to match the review tools:
+    # http://bazaar.launchpad.net/~click-reviewers/click-reviewers-tools/trunk/view/head:/clickreviews/common.py#L38
+    mksquashfs_args = ['-noappend', '-comp', 'xz', '-all-root']
     subprocess.check_call(
-        ['mksquashfs', snap_dir, snap_name, '-noappend', '-comp', 'xz'])
+        ['mksquashfs', snap_dir, snap_name] + mksquashfs_args)
     logger.info('Snapped {}'.format(snap_name))