+++ This bug was initially created as a clone of Bug #830776 +++

Description of problem:
I scheduled kickstart (in WebUI, Satellite 5.4.1) to be picked up after some specified time in expectation that osad running on the host machine would pick up the action at that time. But I ran rhn_check approximately at the same moment and rhn_check failed with traceback (in /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

Version-Release number of selected component (if applicable):
RHEL Server 6.3 x86_64
rhn-client-tools-1.0.0-87.el6.noarch

How reproducible:
always

Steps to Reproduce:
1. in WebUI - schedule kickstart no sooner than some time
2. run rhn_check manually at the same time
3. check logs
  
Actual results:
traceback is shown + logged in /var/log/up2date

Expected results:
localized error message should be shown ("Attempting to run more than one instance of rhn_check. Exiting.")

Additional info:
Simplest fix is to add these lines to /usr/sbin/rhn_check:

import gettext
t = gettext.translation('rhn-client-tools', fallback=True)
_ = t.ugettext