Katello backups fail intermitently, with "no file or directory" errors.

Issue

• Repo Syncs that run while backups are running, intermittently fail with "no file or directory" errors like below:

katello-backup --online-backup /backups/current
Starting backup: 2017-05-21 02:00:02 -0700
Creating backup folder /backups/current/katello-backup-2017-05-21T02:00:02-07:00
Generating metadata ... 
/opt/theforeman/tfm/root/usr/share/gems/gems/foreman_theme_satellite-0.1.42/app/models/concerns/satellite_packages.rb:4: warning: already initialized constant Katello::Ping::PACKAGES
/opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.0.0.124/app/models/katello/ping.rb:7: warning: previous definition of PACKAGES was here
Backing up config files...
Done.
Backing up postgres db...
Done.
Backing up mongo db... 
Done.
Backing up Pulp data...
tar: Removing leading `/' from member names

 tar: /var/lib/pulp/published/yum/master/yum_distributor/ICS-fc25-Updates/1495282297.43: Cannot open: No such file or directory
tar: /var/lib/pulp/published/yum/master/yum_distributor/ICS-fc25-Updates/1495282297.43/drpms: Cannot open: No such file or directory
tar: /var/lib/pulp/published/yum/master/yum_distributor/ICS-fc25-Updates/1495282297.43/repodata: Cannot open: No such file or directory
tar: /var/lib/pulp/published/yum/master/yum_distributor/SMSG-fc25-Updates/1494850607.0: Cannot open: No such file or directory
tar: /var/lib/pulp/published/yum/master/yum_distributor/SMSG-fc25-Updates/1494850607.0/drpms: Cannot open: No such file or directory
tar: /var/lib/pulp/published/yum/master/yum_distributor/SMSG-fc25-Updates/1494850607.0/repodata: Cannot open: No such file or directory
tar: Exiting with failure status due to previous errors
tar: Removing leading `/' from member names
Done.
Done with backup: 2017-05-21 10:18:20 -0700
**** BACKUP Complete, contents can be found in: /backups/current/katello-backup-2017-05-21T02:00:02-07:00 ****
  Backup time: 08:18:19 
Backup Completed: Sun May 21 10:18:20 PDT 2017
tar: Exiting with failure status due to previous errors
Error: 0 (any value except 1 means error)
Null message body; hope that's ok