error() was deprecated back in 2015

[sharpchi]

Noticed the use of error() in a couple of places, this was removed some time ago:

------ --------------------------------------------------------------------- 
  Line   mod/checklist/locallib.php                                  
 ------ ---------------------------------------------------------------------                  
  2002   Function error not found.                                            
  2736   Function error not found.                                            
 ------ --------------------------------------------------------------------- 

Fix:

throw new moodle_exception();