diff -r b77aa48ba690 -r 734515aca84d mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Tue Apr 10 18:13:28 2018 -0700
+++ b/mercurial/debugcommands.py	Tue Apr 10 14:29:15 2018 -0700
@@ -33,6 +33,9 @@
     nullrev,
     short,
 )
+from .thirdparty import (
+    cbor,
+)
 from . import (
     bundle2,
     changegroup,
@@ -3045,9 +3048,14 @@
             req.get_method = lambda: method
 
             try:
-                opener.open(req).read()
+                res = opener.open(req)
+                body = res.read()
             except util.urlerr.urlerror as e:
                 e.read()
+                continue
+
+            if res.headers.get('Content-Type') == 'application/mercurial-cbor':
+                ui.write(_('cbor> %s\n') % stringutil.pprint(cbor.loads(body)))
 
         elif action == 'close':
             peer.close()