`cargo package` is not working

The `cargo package` command results in:

```
   Packaging hello_world v0.0.1 (file:///Users/eduardobautista/Projects/hello_world)
   Verifying hello_world v0.0.1 (file:///Users/eduardobautista/Projects/hello_world)
failed to verify package tarball
```

This is on a newly generated cargo project using the October 31st build `492bc86` on OS X.
