adding a simulation mode

Thu Jul 12 09:20:18 EDT 2012

One thing that I don't quite understand is why some calls even if I
catch the exception still makes the whole program quit.
For example this
 try:
 copytree('sjkdf', 'dsflkj')
 Popen(['notfouhd'], shell=True)
 except Exception as e:
 print("here")
behaves differently from:
 try:
 Popen(['notfouhd'], shell=True)
 copytree('sjkdf', 'dsflkj')
 except Exception as e:
 print("here")
because if copytree fails it quits anyway.
I also looked at the code but can't quite get why.. any idea?