Satellite 6: Client registration fails with "Exception: Error updating system data".

Issue

• Trying to register a system on Red Hat Satellite 6:

subscription-manager register --org="org1" --activationkey="RHEL6_key"
The system has been registered with id: ee340596-2911-4921-acf3-2156c987326b
Error updating system data, see /var/log/rhsm/rhsm.log for more details.

• /var/log/rhsm/rhsm.log

2015-03-04 16:22:08,905 [ERROR]  @cache.py:164 - Error updating system data
2015-03-04 16:22:08,907 [ERROR]  @managercli.py:65 - exception caught in subscription-manager
2015-03-04 16:22:08,907 [ERROR]  @managercli.py:66 - Error updating system data, see /var/log/rhsm/rhsm.log for more details.
Traceback (most recent call last):
  File "/usr/sbin/subscription-manager", line 78, in <module>
    sys.exit(abs(main() or 0))
  File "/usr/sbin/subscription-manager", line 69, in main
    return managercli.CLI().main()
  File "/usr/share/rhsm/subscription_manager/managercli.py", line 1382, in main
    cmd.main()
  File "/usr/share/rhsm/subscription_manager/managercli.py", line 233, in main
    self._do_command()
  File "/usr/share/rhsm/subscription_manager/managercli.py", line 627, in _do_command
    profile_mgr.update_check(admin_cp, consumer['uuid'])
  File "/usr/share/rhsm/subscription_manager/cache.py", line 212, in update_check
    return CacheManager.update_check(self, uep, consumer_uuid)
  File "/usr/share/rhsm/subscription_manager/cache.py", line 166, in update_check
    raise Exception(_("Error updating system data, see /var/log/rhsm/rhsm.log "
Exception: Error updating system data, see /var/log/rhsm/rhsm.log for more details.