pull/releasepull.go
func (r *Release) Read(releaseLocation string) (io.ReadCloser, error) {
	local, err := r.Pull(releaseLocation)
	if err != nil {
		return nil, err
	}
	rr, err := os.Open(local)
	if err != nil {
		return nil, err
	}
	return rr, nil
}
func (r *Release) Read(releaseLocation string) (io.ReadCloser, error) {
	local, err := r.Pull(releaseLocation)
	if err != nil {
		return nil, err
	}
	rr, err := os.Open(local)
	if err != nil {
		return nil, err
	}
	return rr, nil
}
// Read downloads the specified Release to the local cache dir and returns a
// reader to the underyling release package.