code style
use except FileNotFoundError rather than os.path.exists
ianxenvstart.py: use sane variable names
improve ianxenvstart.py
Keep as little in try block as possible
xstart: use os.execlp instead of Popen
Remove code duplication
abook.py use filter to simplify email splitting code
abook.py: use configparser to read addressbook rather than executing
abook