AthenaCommon: Some fixes for athena.py -s
The exclusion pattern for AthenaCommon was failing if AthenaCommon was built in a local WorkArea.
sys.maxint doesn't exist in py3 --- change to maxsize.
With py3, we get _trace_include called with some internal bootstrap methods. We were taking a huge amount of time trying to resolve these with FindFile. Just ignore them instead.