rhn_check fails with an exception "<type 'exceptions.NameError' >" if we are running more than one instances of rhn_check

Issue

• rhn_check fails with an exception <type 'exceptions.NameError'> if we are running more than one instances of rhn_check
• rhn_check command fails with following error :

# rhn_check
An error has occurred:
<type 'exceptions.NameError'>
See /var/log/up2date for more information

[root@test ~]# tail -f /var/log/up2date
Traceback (most recent call last):
  File "/usr/sbin/rhn_check", line 374, in <module>
    cli.run()
  File "/usr/share/rhn/up2date_client/rhncli.py", line 84, in run
    sys.exit(self.main() or 0)
  File "/usr/sbin/rhn_check", line 63, in main
    CheckCli.__check_instance_lock()
  File "/usr/sbin/rhn_check", line 369, in __check_instance_lock
    sys.stderr.write(rhncli.utf8_encode(_("Attempting to run more than one instance of rhn_check. Exiting.\n")))
<type 'exceptions.NameError'>: global name '_' is not defined