Fixing digitization error message irony

Because there was a missing import, these error messages, which are supposed to ressult in a run time error, created a run time error. That's not a huge problem, but this patch makes the crash a little more clear. Fixes one of the issues from ATLMCPROD-8098

Simulation/Digitization/python/DigiConfigCheckers.py

@@ -20,7 +20,7 @@ def checkTRT_DigitizationConfiguration():
 
 
 def checkDetFlagConfiguration():
-    from AthenaCommon.Logging import logging
+    from AthenaCommon.Logging import logging,AthError
     logDigiConfigChecker = logging.getLogger( 'DigiConfigChecker' )
 
     from AthenaCommon.DetFlags import DetFlags