"rake aborted!" email message multiple times a day

I am receiving the following email message multiple times a day:

Date: Mon, 26 Dec 2016 12:00:04 +0000 (UTC)
From: Cron Daemon 
To: root@mudskipper.cdev.bitmask.net
Subject: Cron  cd /srv/leap/webapp && bundle exec rake db:rotate

rake aborted!
RestClient::ServiceUnavailable: 503 Service Unavailable
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/rest-client-1.6.9/lib/restclient/abstract_response.rb:48:in `return!'
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/rest-client-1.6.9/lib/restclient/request.rb:269:in `process_result'
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/rest-client-1.6.9/lib/restclient/request.rb:212:in `block in transmit'
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/rest-client-1.6.9/lib/restclient/request.rb:206:in `transmit'
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/rest-client-1.6.9/lib/restclient/request.rb:68:in `execute'
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/rest-client-1.6.9/lib/restclient/request.rb:35:in `execute'
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/couchrest-1.1.3/lib/couchrest/rest_api.rb:94:in `execute'
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/couchrest-1.1.3/lib/couchrest/rest_api.rb:74:in `head'
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/couchrest_session_store-0.3.1/lib/couchrest/model/database_method.rb:108:in
`database_exists?'
/srv/leap/webapp/vendor/bundle/ruby/2.1.0/gems/couchrest_session_store-0.3.1/lib/couchrest/model/rotation.rb:96:in
`rotate_database_now'
/srv/leap/webapp/lib/tasks/leap_web_core_tasks.rake:49:in `block (2 levels) in '
Tasks: TOP => db:rotate
(See full trace by running task with --trace)

I don't understand what it means, and i also think that the mudskipper node is not active anymore.

(from redmine: created on 2016-12-26)