diff -r 1f65d7d46545 -r d618558e4e8b mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Sat May 05 18:03:01 2018 -0500
+++ b/mercurial/debugcommands.py	Tue May 08 11:39:38 2018 +0200
@@ -352,7 +352,8 @@
     for part in gen.iterparts():
         if parttypes and part.type not in parttypes:
             continue
-        ui.write('%s -- %s\n' % (part.type, _quasirepr(part.params)))
+        msg = '%s -- %s (mandatory: %r)\n'
+        ui.write((msg % (part.type, _quasirepr(part.params), part.mandatory)))
         if part.type == 'changegroup':
             version = part.params.get('version', '01')
             cg = changegroup.getunbundler(version, part, 'UN')