errors are not wrapped

[lugu]

Error messages are hard to reason about since they are hand generated like:

	return fmt.Errorf("call say failed: %s", err)

Go 1.13 provides an helper errors.Wrap which can be used like this:

            return errors.Wrap(err, "say failed")

Please favor errors.Wrap and %w when it makes sense so we would use values for errors like disconnection, authentication failed, remote error...