What is the error reported with "generating secret for digest authentication ..."?

I'm working through our web server's error log for an Open Source project. I see repeated entries for:

$ cat /var/log/httpd/error_log-20160522 | grep "digest"     
[Mon May 16 08:11:29.004792 2016] [auth_digest:notice] [pid 20628] AH01757: generating secret for digest authentication ...
[Thu May 19 09:45:18.519977 2016] [auth_digest:notice] [pid 12588] AH01757: generating secret for digest authentication ...
[Thu May 19 09:47:10.331913 2016] [auth_digest:notice] [pid 128] AH01757: generating secret for digest authentication ...
[Thu May 19 14:59:26.211893 2016] [auth_digest:notice] [pid 7102] AH01757: generating secret for digest authentication ...
...

What, exactly, is the error Apache is reporting? How do I fix it?

---

$ hostnamectl
  ...
    Virtualization: openvz
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Keel: Linux 2.6.32-042stab113.17
      Architecture: x86-64

$ apachectl -V
Server version: Apache/2.4.6 (CentOS)
Server built:   May 12 2016 10:27:23
...

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