Fix lint in unit test

Change-Id: I0921c5508a64e986fe9ad943700276e68fe7e4ba

unit_tests/test_utils.py

@@ -50,7 +50,7 @@ def load_config():
 
     if not config:
         logging.error('Could not find config.yaml in any parent directory '
-                      'of %s. ' % file)
+                      'of %s. ' % __file__)
         raise Exception
 
     return yaml.safe_load(open(config).read())['options']