It's throwing an error because of `error`:
```
---> Making bundle: binary (in bundles/0.10.0-dev/binary)
# github.com/dotcloud/docker/pkg/proxy
pkg/proxy/proxy.go:34: cannot use *TCPProxy as type Proxy in return argument:
        *TCPProxy does not implement Proxy (wrong type for Close method)
                have Close() error
                want Close()
```