I believe we need an auto-update option, something like this:

owtf.py --update

To update:

1. OWTF itself
2. All the restricted tools (i.e. like w3af)

This will prevent out-of-date issues like this:
andresriancho/w3af#351

sqlmap auto-updater for reference:
https://github.com/sqlmapproject/sqlmap/blob/4b9d8ed67304b228f80119070037dc2f5c68b14f/lib/core/update.py

w3af config style auto-update:
https://github.com/andresriancho/w3af/blob/f3b0667bf65a87d16dc0066a53b7a17945c9b98b/core/data/db/startup_cfg.py