problem with hidden (amend commit) and a hook

[Uwe Brauer]

Hi 

I just pushed and received the following hg push
pushing to https://kalthad@bitbucket.org/kalthad/contflowmap
searching for changes
 ChangeLog                      |    24 ++-
 20 files changed, 2647 insertions(+), 1038 deletions(-)
error: outgoing.notify hook raised an exception: hidden revision '317'
(run with --traceback for stack trace)

But it seemed that the push went ok, when I rerun 

 hg push --traceback

As recommended I obtained: no changes found.

Is this serious? How can I avoid that message?

I have
[hooks]
outgoing=hg diff --stat -r "p1($HG_NODE)" -r "max(descendants($HG_NODE))"

And locally 
outgoing.notify = python:hgext.notify.hook

Running on Ubuntu 16.06: mercurial  4.4.1  (which is not the  official
ubuntu mercurial version)