- If during an action, user does not exist ignore.
- If during an action, return a non-zero exist status.
- Catch an errors during actions as exceptions.
- Display a message that corresponding POSIX operation failed.
We manually have to call the form.save() method in form_valid().
Plus tiny cleanups like using SetPasswordForm instead of
AdminPasswordChangeForm.
Note: this allows any logged-in user to change all other user passwords.
- allows editing users (currently the groups and username)
- allows any logged-in user to change the passwords of any other users
- improved url highlighting of subsubmenu
