dtruss.py: deal with optional argument in the python way
dtruss.py: deal with optional argument in the python way

cuckoobox/cuckoo,rodionovd/cuckoo-osx-analyzer,cuckoobox/cuckoo,cuckoobox/cuckoo,cuckoobox/cuckoo,cuckoobox/cuckoo,rodionovd/cuckoo-osx-analyzer,rodionovd/cuckoo-osx-analyzer