dotcloud/docker — pull request #4566 by srid (2014-03-10 23:52:07+00:00)
Title: nsinit: prefix errors with their source

otherwise it is hard to find where an error is coming from. i decided do this after seeing the "invalid argument" error from nsinit. after this change, i get:

```
2014/03/10 16:51:30 Failed to execute: invalid argument
```