Fix gate problem related to  _error_checker()

Since I84e3be748af10b158037866e1ee4c1375b2c3541, the internal method
_error_checker() is changed and the ceilometer gate is broken.
This patch fixes it.

Change-Id: I83a4899227e117e8f05ad179e5656ef6784f4a0b
1 file changed
tree: 57f0c9c17cdbffc83999d6a54ce168dc452d79fb
  1. ceilometer/