Python os.system module handle errors

Hi all,

When I create a database dump in python script and if there are some errors (user_name is not correct, db_name doesn't
existor something else) I need to send e-mail notification to admin. How can I handle these errors?
 

Example:
----------------------------------------------------------------------------#!/usr/bin/python
import os

os.system("pg_dump -U user_name -i -F c -v db_name -f file_name.backup") 
print "%s backup complete" % ("Database XXX")
----------------------------------------------------------------------------

I tried to use, but it doesn't work.

----------------------------------------------------------------------------
#!/usr/bin/python
import os

try:
    os.system("pg_dump -U user_name -i -F c -v db_name -f file_name.backup")
    print "%s backup complete" % ("Database XXX")
except os.error:

    # ...
    # here sending e-mail if there is an error of backing up
    # ...

    print "Backup error %s" % error


--
Vadim