How can I capture all exceptions especially when os.system() fail? Thanks

[mike]

Hi Guys,

Following piece of code can capture IOError when the file doesn't
exist, also, other unknown exceptions can be captured when I press
Ctrl-C while the program is sleeping(time.sleep). Now the question is:
when I run the non-exist command, the exception cannot be captured.

Here is the code:
===================================
#!/usr/bin/python
import os
import sys
import time

try:
    fh = open("tt.py")
    time.sleep(10)
    #os.system("wrong_command_test")
except IOError:
    print 'failed to open.'
    sys.exit(0)
except:
    print 'Some exceptions occurred.'
else:
    print 'well',

print 'Done'

===================================
when the tt.py doesn't exist, the script printed:
failed to open.
when the tt.py exists, the script printed:
well done
when I press Ctrl-C while the program is sleeping, the script printed:
Some exceptions occurred.
Done

So far so good, then I changed the code to run a non-exist command
"wrong_command_test"(commented the open and sleep lines), then the
script printed:
sh: wrong_command_test: command not found
well Done


Any opinions would be appreciated.

Mike