ginatrapani/todo.txt-cli — pull request #59 by inkarkat (2011-12-17 22:28:18+00:00)
Title: BUG: pri doesn't issue an error when the task does not exist. 

```
$ tt pri 999 b
999
TODO: 999 prioritized (B).
```

I've verified that all other built-in actions do check this. As a bonus, I've thrown in a refactoring that eliminates the duplicated retrieval of task texts, and exports this functionality for custom add-ons, too.