Handling errors with RxJava and Retrofit

Converter<ResponseBody, Error> errorConverter =
        ServiceGenerator.retrofit.responseBodyConverter(Error.class, new Annotation[0]);
try {
    Error error = errorConverter.convert(response.errorBody());

    if (error.getCode().equals(ERROR_STATUS)) {
        if (!inputUsername.requestFocus()) {
            inputUsername.requestFocus();
        }
        Toast.makeText(SignUpActivty.this, getString(R.string.sign_up_username_exists), Toast.LENGTH_LONG).show();
    }
} catch (IOException e) {
    e.printStackTrace();
}