diff -r b2fa1591fb44 -r 8cea0d57bf37 mercurial/httppeer.py
--- a/mercurial/httppeer.py	Fri Apr 13 12:31:56 2018 -0700
+++ b/mercurial/httppeer.py	Thu Apr 12 13:08:33 2018 -0700
@@ -763,6 +763,14 @@
                     f.set_result(result)
                     del results[request.requestid]
 
+            elif action == 'error':
+                e = error.RepoError(meta['message'])
+
+                if f:
+                    f.set_exception(e)
+                else:
+                    raise e
+
             else:
                 e = error.ProgrammingError('unhandled action: %s' % action)