Updating package lists is required for the first time, I think the warning tries to cope with package upgrades.

Nowadays Ubuntu does a better job keeping package lists uptodate automatically, the warning may be more confusing than useful.

what about removing it or go for something like:

```
.. note:: Please note that these packages are updated frequently. If you are trying 
   to upgrade Scrapy, run ``sudo apt-get update`` to update package list first.
```