custom grain __salt__

foograin.py

def __virtual__():
    return "my_grain"

def my_grain():
    grains = {}
    test = __salt__['cmd.run']("awk '{/test/; print $2}' /tmp/foo.txt")
    grains['my_grain'] = test
    return grains

minion_log

CRITICAL] Failed to load grains defined in grain file my_grain.my_grain in function <function my_grain at 0x2b70578>, error:
Traceback (most recent call last):
  File "/home/jeremy.alons/linux/venv/lib/python2.7/site-packages/salt/loader.py", line 911, in gen_grains
    ret = fun()
  File "/home/jeremy.alons/linux/salt/var/cache/salt/minion/extmods/grains/foograin.py", line 6, in my_grain
    test = __salt__['cmd.run']("awk '{/test/; print $2}' /tmp/foo.txt")
KeyError: 'cmd.run'