Spacewalk? error /XMLRPC/GET-REQ/ol6_x86_64_latest/repodata/repomd.xml

On my Spacewalk 2.4 server logwatch reported the following error:

--------------------- httpd Begin ------------------------

Requests with error response codes

    401 Unauthorized

       /XMLRPC/GET-REQ/ol6_x86_64_latest/repodata/repomd.xml: 1 Time(s)

---------------------- httpd End -------------------------

but I do not see any errors on the Spacewalk log:

sudo tail /var/log/rhn/reposync/ol6_x86_64_latest.log

Sync started: Thu Apr 13 05:00:00 2017

['/usr/bin/spacewalk-repo-sync', '--channel', 'ol6_x86_64_latest', '--type', 'yum']

Repo URL: uln:///ol6_x86_64_latest

Packages in repo:             38784

No new packages to sync.

Repo uln:///ol6_x86_64_latest has comps file comps.xml.

Repo uln:///ol6_x86_64_latest has 2883 errata.

Sync completed.