I'd keep both scripts documented, as some people may play with that without having access to the VM.

With the usage of stderr, we can suggest doing: python2.7 fetch_amo.py 2 > errors.txt.
And I'd rather keep a normalized folder layout and keep mkdir/cd commands.
``` 
$ mkdir /addons/ftp
$ cd /addons
$ python2.7 scripts/fetch_amo.py
... download xpi files to /addons/ftp ...
```