private static Reader readerFromFile(URL resourceUrl) throws IOException, URISyntaxException {
    File resourceFile = new File(resourceUrl.toURI());
    return new InputStreamReader(new FileInputStream(resourceFile), UTF_8);
  }
Returns the result of substituting the variables defined by the fields of this class (a
concrete subclass of TemplateVars) into the template returned by {@link #parsedTemplate()}.
value/src/main/java/com/google/auto/value/processor/TemplateVars.java