--- a/mercurial/commands.py	Mon Sep 14 19:25:34 2015 -0400
+++ b/mercurial/commands.py	Fri Sep 25 23:10:47 2015 -0500
@@ -6388,6 +6388,12 @@
                 try:
                     op = bundle2.processbundle(repo, gen, lambda: tr)
                     tr.close()
+                except error.UnsupportedPartError as exc:
+                    raise util.Abort(_('%s: unknown bundle feature, %s')
+                                     % (fname, exc),
+                                     hint=_("see https://mercurial.selenic.com/"
+                                            "wiki/BundleFeature for more "
+                                            "information"))
                 finally:
                     if tr:
                         tr.release()